LOS ANGELES — The chief executive of Sony’s underperforming entertainment division, Michael Lynton, announced Friday that he would step down to focus more intently on the popular messaging service Snapchat, where he was an early investor.

Mr. Lynton, who weathered various corporate crises at Sony Entertainment over his 13-year tenure, including a devastating cyberattack and a battle with activist investors, will step down on Feb. 2, the company said. After that, Kazuo Hirai, the president and chief executive of Sony Corporation, based in Tokyo, will take a more hands-on role at the conglomerate’s movie, television and music division, at least for a time.

Mr. Hirai will begin keeping a second office at Sony’s studio complex in Culver City, Calif., the company said, and take the additional title of co-chief executive of Sony Entertainment. Mr. Lynton will also serve as co-chief executive for a six-month period starting in February to help Mr. Hirai learn the inner workings of the fast-changing movie and television businesses and select a permanent successor.

In the meantime, Mr. Lynton, 57, will officially become chairman of the board at Snap Inc., which owns Snapchat. Snap is expected to go public — with an eye toward being valued at $30 billion or more — this spring. As chairman, Mr. Lynton is not expected to play a direct management role, but rather focus on matters involving strategy and governance in support of Evan Spiegel, Snap’s chief executive.