The 41-year-old actor said that he has become fascinated by the mechanics of the bike and enjoys surfing the internet auction site to find frames to work on, reported Daily Star online.
"You buy a frame on eBay, and you think, 'What do I do now?' You have your aesthetic idea, but all bike builders say it kind of builds itself - which it does in a way.
Things either do or don't work. Components fit or they don't, and sometimes you alter them until they do," he said.
However, McGregor has little use for all of the bikes he has been building at his Los Angeles home - because everyone drives in California.
"At the end of the day, you've built a work of art, but you can also ride it to the shops. (Only) nobody rides bikes in LA," McGregor added.