Microsoft’s own Windows-powered phones have left to make a meaningful impact on the smartphone market, which is controlled by devices running Google’s Android operating system.
However, Mr. Gates said he had been using lots of Microsoft apps on his phone.
When questioned whether he also had an iPhone, possibly as a secondary device, he replied: “No, no iPhone.”
He did not reveal which particular smartphone he currently uses.
Microsoft tried to gain a success of its own mobile operating system, Windows Phone.
In 2014, the software titan paid $7.2bn (£5.5bn) for Nokia’s handset business, but Windows-powered receivers accounted for fewer than 1% of global smartphone sales in 2016.
Microsoft’s latest operating system, Windows 10, can power smartphones in addition to laptops, tablets and desktop computers. However, few Windows 10 smartphones have been released.
In April, Microsoft began selling a customised variant of Samsung’s Galaxy 8 smartphone in its US stores.
“Microsoft’s strategy following its current chief executive Satya Nadella is to make Microsoft apps and settings widely available on Android and iPhone,” said Ian Fogg, an analyst at the tech consultancy IHS Markit.
“That’s where their consumers are these days.”
The “Microsoft Edition” phone appears with the firm’s apps such as Office, Outlook email and its voice assistant Cortana included.