Buffett was asked about whether Gates might return to Microsoft when current CEO Steve Ballmer retires in less than a year during an appearance on Bloomberg television Tuesday.
Buffett says Gates is doing what he loves leading the Bill & Melinda Gates Foundation, and he has more than a full-time job with the charity.
Buffett and Gates are close friends, and Buffett has entrusted the Gates Foundation with giving away the bulk of his fortune over time. Gates also serves on the board of Buffett's Berkshire Hathaway Inc. conglomerate.
In related news, Oracle President Mark Hurd says he's not planning on becoming Microsoft's next CEO. Hurd tells CNBC that he's happy at the business software maker and doesn't expect to be going anywhere.
Microsoft Corp. CEO Steve Ballmer announced in August that he planned to step down as head of the Redmond, Wash., company within the next year.
Hurd's name has been floated as a possible replacement. Other potential candidates include current Ford Motor Co. CEO Alan Mulally.