According to some reports, the Chinese authorities agreed to accept the man - believed to be Kim Jong-nam - as part of a deal to avoid a diplomatic incident.
The man, along with two women and a four-year-old boy who had arrived in the country with him, boarded an All Nippon Airways flight bound for Beijing.
According to some reports, the Chinese authorities agreed to accept the man - believed to be Kim Jong-nam - as part of a deal to avoid a diplomatic incident.
He had been in custody since Tuesday, when he arrived at Tokyo's Narita International Airport and admitted that he had paid $2,000 each for the fake passports for him and his travelling companions. He said he wanted to visit Tokyo Disneyland.
Japan has no diplomatic relations with North Korea and has been alarmed by the country's missile tests in recent years.
If the man is actually Kim Jong-nam, he is the likely heir to North Korea's reclusive leader, Kim Jong-il.
BBC Tokyo correspondent Charles Scanlon says that the fact that he is being sent to China indicates that the authorities believe his story.
Little is known about the family of Kim Jong-il, but South Korean sources say he has three children by three different women.
Kim Jong-nam, the eldest, is believed to have been born in 1971 to Sung Hae Rim, who apparently never married his father.
More recent reports suggest she is in Moscow, receiving treatment for depression.
The North Korean leader's official wife is Kim Young Sook, the mother of Mr Kim's only daughter, Kim Sul Song.
Travel difficulties
Kim Jong-nam spent part of his childhood in Geneva and Moscow, and is thought to be a computer expert.
He is reported to have travelled to Japan twice last year. But correspondents say North Korea's diplomatic isolation would make it difficult for Kim Jong-nam to enter the country under his own identity.
Pyongyang only has diplomatic relations with a handful of Western countries, so North Koreans may have little option but to use forged passports and make their journeys clandestinely.
Experts say that North Korea is a known source of forged passports and counterfeit dollars.