"For someone on the Supreme Court who is going to be calling balls and strikes in the future based upon what the next president and Congress does, that strikes me as inherently biased and out of the realm," Ryan said on CNN Tuesday evening in a town hall interview.
In a series of interviews earlier this week, Ginsburg referred to Trump as a "faker" and called on him to release his tax returns.
"I can't imagine what the country would be - with Donald Trump as our president," she told the New York Times.
"That shows bias to me," Ryan said of the comments, describing them as "out of place" for a top judge.
Ryan was also sharply questioned about his endorsement of Donald Trump, and argued that the election is a "binary choice."
"We have a binary choice: Donald Trump, Hillary Clinton. The Libertarian is basically voting for Hillary Clinton," he said.
Ryan also argued that not supporting Trump would have split the Republican Party -- and potentially swing the Supreme Court to the left for a generation.
Asked by the daughter of a Fort Hood shooting victim how he could support Trump given his proposed Muslim immigration ban, Ryan said he splits with Trump on the issue.
"The good clearly outweighs the things I don't agree with," Ryan said of Trump. "That's just the way it works in government, in politics. We don't have people who run for office who 100 percent reflect all of our views. We have to find people who reflect most of our views."
The Wisconsin Republican said Trump is more likely to enact the House GOP election-year agenda than Clinton.