UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER

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

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of February 2018

Commission File Number: 000-53445

KB Financial Group Inc.

(Translation of registrant’s name into English)

26, Gukjegeumyung-ro 8-gil, Yeongdeungpo-gu, Seoul 07331, 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.

Preliminary Operating Results for Fiscal Year 2017

On February 8, 2018, KB Financial Group Inc. (“KB Financial Group”) held an earnings conference and released its preliminary operating results for fiscal year 2017. The following tables reflect the key figures released during the conference. The presentation materials for the conference, which contain further details, are available at KB Financial Group’s website (http://www.kbfg.com).

The preliminary figures presented herein are based on the International Financial Reporting Standards as adopted by the Republic of Korea (“K-IFRS”) and are currently being audited by KB Financial Group’s independent auditors and are subject to change.

Declaration of Cash Dividends by KB Financial Group

On February 8, 2018, the board of directors of KB Financial Group passed a resolution to declare a cash dividend of KRW1,920 per common share(total dividend amount: KRW766,728,159,360), subject to shareholder approval. The record date is December 31, 2017, and in accordance with the Korean Commercial Code, the payment for such dividends is expected to be made within one month following shareholder approval at the annual general meeting of shareholders of KB Financial Group.

The contents of the above declaration remain subject to change pending approval at the annual general meeting of shareholders and the results of the audit by KB Financial Group’s independent auditors.

The total number of common shares that are eligible for payment of dividends is 399,337,583 shares.

Declaration of Cash Dividends by Kookmin Bank

On February 7, 2018, the board of directors of Kookmin Bank, a wholly-owned subsidiary of KB Financial Group, passed a resolution to declare a cash dividend of KRW1,583 per common share (total dividend amount: KRW640,132,140,628), subject to shareholder approval. The record date is December 31, 2017, and in accordance with the Korean Commercial Code, the payment for such dividends is expected to be made within one month following shareholder approval at the annual general meeting of shareholders of Kookmin Bank, which is expected to be held on March 22, 2018. The entire dividend amount is to be paid to KB Financial Group, which holds all of the common shares of Kookmin Bank.

The contents of the above declaration remain subject to change pending approval at the annual general meeting of shareholders of Kookmin Bank and the results of the audit of Kookmin Bank by its independent auditors.

Declaration of Cash Dividends by KB Securities

On February 7, 2018, the board of directors of KB Securities, a wholly-owned subsidiary of KB Financial Group, passed a resolution to declare a cash dividend of KRW466 per common share (total dividend amount: KRW139,157,117,584), subject to shareholder approval. The record date is December 31, 2017, and in accordance with the Korean Commercial Code, the payment for such dividends is expected to be made within one month following shareholder approval at the annual general meeting of shareholders of KB Securities, which is expected to be held on March 22, 2018.

The contents of the above declaration remain subject to change pending approval at the annual general meeting of shareholders of KB Securities and the results of the audit of KB Securities by its independent auditors.

Report of Change in Revenue or Profit of More than 15% (KB Financial Group)

On February 8, 2018, KB Financial Group disclosed changes in its revenue and profit as described below.

Report of Change in Revenue or Profit of More than 15% (Kookmin Bank)

On February 8, 2018, KB Financial Group disclosed changes in its revenue and profit of Kookmin Bank as described below.

Report of Change in Revenue or Profit of More than 15% (KB Securities)

On February 8, 2018, KB Financial Group disclosed changes in its revenue and profit of KB Securities as described below.

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.