Buffett declined to answer whether he's buying even more, but said, "I certainly was buying last quarter and I don't pay attention to the calendar when I'm buying."
When Berkshire first made an investment in Apple in 2016 a fellow at Berkshire bought about 10 million shares, Buffett said. "And then, I looked at it, and I bought considerably more," he said.
The fellow he was referring to was likely either Todd Combs or Ted Weschler, money managers at Berkshire. But Buffett refused to say which one.
After Jan. 1, 2016, and before Apple reported earnings on Jan. 31, Buffett's Berkshire added almost 76 million Apple shares to its holdings. Asked at the time why, he said, "Because I liked it."
As of June 30, 2017, regulatory filings show Berkshire has amassed 130.2 million shares of Apple.
On Wednesday, the tech giant's stock was around $162 per share and hit a record high shortly after the open.
Based on a $162 share price, Berkshire's Apple stake was worth about $21.1 billion.
Buffett told CNBC he's more certain about Apple's future than IBM.
Berkshire had owned about 81 million shares of IBM at the end of 2016, but sold off about a third of that stake in the first and second quarters of 2017.
"I don't value IBM the same way that I did six years ago when I started buying," Buffett told CNBC in May. "I've revalued it somewhat downward.