SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K/A

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of May 2017

Commission File Number: 000-53445

KB Financial Group Inc.

(Translation of registrant’s name into English)

84, Namdaemoon-ro, Jung-gu, Seoul, 04534, Korea

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F  ☒             Form 40-F  ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ☐

Note: Regulation S-T Rule 101(b)(1) only permits the submission in paper of a Form 6-K if submitted solely to provide an attached annual report to security holders.

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ☐

Note: Regulation S-T Rule 101(b)(7) only permits the submission in paper of a Form 6-K if submitted to furnish a report or other document that the registrant foreign private issuer must furnish and make public under the laws of the jurisdiction in which the registrant is incorporated, domiciled or legally organized (the registrant’s “home country”), or under the rules of the home country exchange on which the registrant’s securities are traded, as long as the report or other document is not a press release, is not required to be and has not been distributed to the registrant’s security holders, and, if discussing a material event, has already been the subject of a Form 6-K submission or other Commission filing on EDGAR.

EXPLANATORY NOTE

This Report of Foreign Private Issuer on Form 6-K/A (this “Amended Report”) is furnished to amend the Report of Foreign Private Issuer furnished to the Securities and Exchange Commission on April 14, 2017 (the “Original Report”). This Amended Report amends the Original Report to (i) update paragraphs a. and b. under “7. Main Impact and Effects of the Stock Swap” to reflect that treasury shares of KB Financial Group Inc. (“KB Financial Group”) have been determined to be transferred to the shareholders of KB Insurance Co., Ltd. (“KB Insurance”) in connection with the Stock Swap (as defined in the Original Report), (ii) under “8. Schedule for the Stock Swap,” amend (a) the date of the Stock Swap to July 7, 2017, (b) the expected date of delivery of share certificates to July 20, 2017 and (c) the expected date of listing of new shares to July 21, 2017, (iii) add a footnote relating to the definitions of certain dates under “8. Schedule for the Stock Swap,” (iv) update paragraph a. and delete paragraph f. under “16. Other Investment Considerations” to reflect the completion of the Tender Offer (as defined in the Original Report) and (v) update paragraph d. under “16. Other Investment Considerations” to indicate that the dissent filing period for the Stock Swap expired on May 11, 2017 and that the Stock Swap will proceed as a small-scale stock swap as the number of shares owned by shareholders who provided notice of their opposition to the Stock Swap during the dissent filing period amounted to less than 20% of the total number of issued shares of KB Financial Group. No other change to the Original Report is made by this Amended Report.

The information set forth in “7. Main Impact and Effects of the Stock Swap,” “8. Schedule for the Stock Swap,” and “16. Other Investment Considerations” of the Original Report is amended and replaced as follows:

Following the results of Tender Offer, which was completed on May 12, 2017, the shares to be transferred to the shareholders of KB Insurance in connection with the Stock Swap have been determined to be treasury shares held by KB Financial Group. As no new shares shall be issued for the Stock Swap, the Stock Swap will not have a dilutive effect on the share ownership percentages of the existing shareholders of KB Financial Group. There will be no change in control for corporate governance purposes, and KB Financial Group and KB Insurance will continue to exist as separate entities.

In addition, pursuant to the Stock Swap Agreement, the terms of office of the directors and audit committee members of KB Financial Group who were appointed prior to the Stock Swap will remain the same following the Stock Swap notwithstanding Article 360-13 of the KCC. No new directors will be appointed as a result of the Stock Swap.

KB Financial Group expects that the Stock Swap, which will entail the disposal of its treasury shares resulting in an increase in its equity, will lead to the improvement of certain of its group-level performance metrics (including its return on equity, double leverage ratio and debt ratio).

Although the assets and liabilities of KB Insurance will remain unchanged and only its shareholder composition will change, KB Insurance expects that the Stock Swap will lead to an improvement of its creditworthiness and the strengthening of its competitiveness pursuant to a stabilization of its ownership structure, as well as the ability to raise capital on more favorable terms if a capital increase is necessary.

By converting KB Insurance to a wholly-owned subsidiary through the Stock Swap, KB Financial Group expects to be able to adopt an efficient management structure that can flexibly respond to regulatory developments and other changes to its business environment and to promote sustainable growth by contributing to the maximization of synergies among affiliated companies of KB Financial Group, through an increase in customer convenience and benefits and the strengthening of its competitiveness.

Note) “Expected date of delivery of share certificates” and “Expected date of listing of new shares” in the table above refer to the expected date of delivery of share certificates for KB Financial Group’s treasury shares and the expected date of the commencement of trading of such treasury shares, respectively.

As a result of the Tender Offer, KB Financial Group currently owns 62,710,408 common shares (94.3% of total issued common shares) of KB Insurance. Accordingly, no new shares shall be issued by KB Financial Group and treasury shares held by KB Financial Group will be transferred to the shareholders of KB Insurance as consideration for the Stock Swap.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.