The story takes place in Metro City, circa 2000 A.D. After the death of his son, Dr. Tenma (Dr. Boynton) copes with his grief by creating a robot child that looks like his son: Astro Boy. After some time it becomes clear that Astro is not like Tobi, so his father sells him to Hamegg (Cacciatore), the cruel ringmaster of a robotic circus. At the circus, Astro is forced to fight against Z.O.G. and wins after he discovers some of his abilities. Professor Ochanomizu (Dr. Elefun) protests the abuse of robots and unsuccessfully negotiates for Astro's release. Later that night, Astro revives some robotics that Hamegg plans to sell as scrap metal. Later a robot named Sparky explodes, causing the whole circus tent to collapse. Astro leads the robots in a rescue mission. Later at a hospital, Astro is liberated from Hamegg as Professor Ochanomizu leaves with him.

Astro Boy longs to have parents, so Professor Ochanomizu has robot parents custom made. In a robotic factory, an experimental robotic named Frankenstein (Colosso) goes haywire and escapes. Frankenstein becomes the slave of a gang led by Acetylene Lamp (Big Boss), who has Frankenstein steal from a safe, a ballet, and a bank. Astro is blamed by Inspector Tawashi (Inspector Gumshoe) for the crimes, but is saved by Professor Ochanomizu. Professor Ochanomizu devises a plan to bait Frankenstein onto a ship using fake diamonds, where Astro defeats Frankenstein. The mobsters arrive, but Astro defeats them and they are soon arrested. Astro is rewarded for his heroism with his recently completed parents. Frankenstein is repaired.

When the first expedition to Mars fails because of a mutiny by the crew, Astro Boy is appointed commander of the second expedition.

Astro Boy and Professor Ochanomizu investigate the disappearances of campers and mountaineers in the ice mountains, and discover a scientist who unleashes a swarm of snails on the world.

Astro Boy is tricked by some bandits into helping them search for treasure in the Egyptian desert.

Higeoyaji is relaxing at home when suddenly a mysterious ship from the future crashes through his front door, the work of Dr. Time.