Keith Block, co-chief executive officer of Salesforce, San Francisco’s largest private employer, has stepped down.

Company co-founder Marc Benioff, with whom Block shared responsibilities, will become sole CEO and remain chairman. Block is staying on as an adviser through next February.

“It’s been my greatest honor to lead the team with Marc that has more than quadrupled Salesforce from $4 billion of revenue when I joined in 2013 to over $17 billion last year,” Block said in a statement. “We are now a global enterprise company, focused on industries, and have an ecosystem that is the envy of the industry, and I’m so grateful to our employees, customers, and partners.”

Block was named co-CEO in 2018, overseeing sales and operations.

Block was formerly Salesforce’s chief operating officer. Before that, he worked at Salesforce's rival Oracle, where Benioff also was an executive before starting Salesforce in 1999.

Salesforce has more than 9,000 employees in San Francisco and is headquartered in the city’s tallest building, Salesforce Tower. The company’s annual 171,000-person Dreamforce conference in the fall is the city’s largest convention.

Benioff decided to share the CEO role after realizing that he was too busy, CNBC reported in 2018. He has become increasingly active in political and social issues, such as leading the winning 2018 Proposition C campaign, which raised San Francisco taxes on large employers including Salesforce in order to fund homelessness measures. Benioff and his wife, Lynne, also bought Time magazine that year.

Salesforce shares dropped 3.5% in after-hours trading. The company also reported earnings for the fourth quarter Tuesday, with revenue at $4.85 billion, above analyst expectations, but a wider loss than expected at $248 million or 28 cents per share.

Roland Li is a San Francisco Chronicle staff writer. Email: roland.li@sfchronicle.com Twitter: @rolandlisf