The British billionaire made the announcement on his blog, saying he gave the actor a quick call to congratulate him.
"He is as thrilled as we are at the prospect of being among the first to cross the final frontier (and back!) with us and to experience the magic of space for himself," Branson wrote.
A representative for Kutcher did not immediately return a message seeking comment.
Kutcher is among dozens of Hollywood types, international entrepreneurs, scientists, space buffs and others who have made deposits to be among the first to reach the edge of the Earth on Branson's Virgin Galactic space line.
Branson has said the aim is to one day make travelling to space safe and affordable for the masses, not just those who can afford the current $200,000 ticket price.
Virgin Galactic is in the final stages of its test flight program. The company will launch its spacecraft from Spaceport America, a specially designed terminal and runway built in a remote stretch of desert in southern New Mexico.
The company plans to begin commercial operations next year. Branson said he and his children plan to be on the first commercial flight.
Christine Anderson, executive director of the New Mexico Spaceport Authority, congratulated Virgin Galactic on Monday for selling its 500th ticket. She said she's looking forward to "the beginning of the commercial passenger space line industry."
Virgin Galactic customers will ride in a six-seat spacecraft that looks like a small plane, with wings near the rear that sweep upward. Once the craft and its mother ship reach a certain altitude, the smaller craft is released and its rockets are fired, pushing passengers back into their seats for the trip to suborbital space.
The spaceship features two large windows for each passenger, one on the side and one overhead, and small thrusters that allow the two pilots to manoeuvr the ship once in space.
Customers will get a 2 1/2-hour flight with about five minutes of weightlessness and views of Earth that until now only astronauts have been able to experience.
"I still sometimes have to pinch myself that it's for real," Branson said of the venture. "Ashton is joining a fast expanding group of true pioneers who are on their way to a life changing experience and a place in the history books."
Follow Susan Montoya Bryan on Twitter: http://www.twitter.com/susanmbryanNM .