Bach, the president of the International Olympic Committee, also said the IOC will make a proposal for a "potential joint march" and other shared activities between the North and South Korean teams at the Tokyo games.
Last month's Winter Olympics in South Korea saw competitors from the two countries march together at the opening ceremony and field a joint women's ice hockey team.
The Winter Games triggered a fast-moving rapprochement that will see Kim sit down with the South's President Moon Jae-in in late April - with a US summit with President Donald Trump planned for May.
Bach told reporters after landing in Beijing that his talks with Kim on Friday had been "very open and fruitful".
|Kim Jong-un (right) meets International Olympic Committee President Thomas Bach in Pyongyang, thanking him for helping to bring about a "dramatic thawing" of tensions on the Korean peninsula, North Korea's state media said on March 31. (Yonhap)|
"They announced (to) us that they will definitely participate in the Olympic Games Tokyo 2020 as well at the Olympic Winter Games Beijing 2022" and all editions of the Youth Olympic Games, Bach said.
"And this commitment was fully supported by the supreme leader of DPRK," he said, using the official abbreviation for the country.
North Korea's official KCNA news agency said Kim thanked Bach for helping to bring about a "dramatic thawing" of tensions on the Korean peninsula.
Bach arrived in the country on Thursday and his visit, which concluded Saturday, was the result of an invitation extended by Pyongyang in January.
The isolated regime rarely hosts foreign dignitaries but recent weeks have seen a flurry of diplomacy, with Kim making his first foreign trip as leader to meet Chinese President Xi Jinping and inviting him to visit Pyongyang.
Kim told Bach that the Olympics had "opened a new chapter of concord between the north and the south", KCNA said.
"He said that the once frozen north-south relations greeted a dramatic thawing season with the Olympics as a momentum and it was totally attributable to the efforts of the IOC which offered an opportunity and paved a path for it," the agency reported.
|International Olympic Committee President Thomas Bach (AFP)|
Bach told reporters the IOC "will continue to support the athletes from DPRK to prepare well" for the next Olympic Games.
"The IOC will make a proposal for a potential joint march, for potential other joint activities for Tokyo and maybe also for Beijing, at the appropriate time," he said.
The two men also held discussions about the development of sport in the North and attended a women's football match.
North and South Korea plan to hold a summit on April 27.
Trump is then due to meet Kim before the end of May for talks on Pyongyang's denuclearisation.
Bach has hailed the reconciliatory mood, saying previously that the Olympic spirit "brought two sides together" and the two neighbours sent a "powerful message of peace" to the world. (AFP)