Robert Park's release clears an obstacle between North Korea and the United States, its main adversary, as pressure mounts on Pyongyang to end its year-long boycott of international nuclear disarmament-for-aid talks.
As Park arrived in Beijing, a senior Chinese official departed for North Korea and was expected to meet the reclusive state's leader, Kim Jong-il.
Park, 28, walked with his eyes practically closed past shouting reporters at Beijing's airport, saying nothing as he was guided by U.S. embassy officials into a car. He will fly back later on Saturday to the United States, an official with the U.S. embassy in Beijing said.
Park was detained after he walked over the frozen Tumen river from China into North Korea on December 25 on what he said was a mission to raise 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, showing sincere repentance.
North Korea said in late January that it was holding a second American for illegal entry. The man has not been identified.
The official Xinhua news agency said Chinese Communist Party international affairs chief Wang Jiarui flew to North Korea at the invitation of the ruling Workers' Party of Korea.
The Chinese visit appears to be a move to press Pyongyang to return to nuclear disarmament talks, South Korean media reported on Friday.
Wang met Kim Jong-Il last year.
China, the destitute North's biggest benefactor, is seen as having the most influence on the reclusive state. Kim Jong-il told the Chinese premier in October he could return to the nuclear talks if conditions were right.
U.N. sanctions imposed after the North's nuclear test last year have dealt an economic blow, and a botched currency reform measure undertaken late last year deepened its financial woes.
(Writing by Jon Herskovitz in Seoul; Reporting by Tyra Dempster and Lucy Hornby in Beijing, Jacqueline Wong in Shanghai and Kim Yeon-hee in Seoul; Editing by Bill Tarrant)