Park's release clears an obstacle between North Korea and the US as pressure mounts on the former to end its year-long boycott of international nuclear disarmament-for-aid talks.
In another North Korea-related development, the South Korean media said a senior Chinese Communist Party official would visit Pyongyang as early as Saturday in what appears to be a move to press it to return to nuclear disarmament talks.
North Korea said on Friday it would release Park, who had said his journey was aimed at raising awareness about Pyongyang's human-rights abuses.
The North's official KCNA news agency said Park had confessed to illegally entering the state and that he had changed his mind about North Korea after receiving kind treatment there.
The North Korean government "decided to leniently forgive and release him, taking his admission and sincere repentance of his wrongdoings into consideration", the official Korean Central News Agency said.
The report quoted Park, of Tucson, Arizona, as saying he was ashamed of the "biased" view he once held of the communist nation.
Duty as Christian
Park told the Reuters news agency in Seoul before he crossed into North Korea that it was his duty as a Christian to make the trip.
He also said he was carrying a letter calling on Kim Jong-il, the North Korean leader, to release those he holds in political camps and to step down.
Interviewed over phone, the Reverend Madison Shockley, a Park family pastor in Carlsbad, California, said: "We are just elated that he's been released safely.
"We cannot wait for him to land on American soil and to hear the truth of what he discovered there."
Shockley said Park's parents were told of the release by the state department on Friday, saying they were in shock, but very happy.