It is still not clear whether the boy was pushed or fell from the window.
The boy survived the fall but is in a critical condition. He is being treated in the Necker hospital in Paris.
The incident happened late on Monday morning in La Courneuve, north of Paris, according to newspaper Le Parisien. The boy and his 6-year-old sister were alone in the apartment with their father.
The newspaper reported that the incident took place after a family dispute during which the boy was tied up as punishment after stealing an MP3 player from a friend.
“This is a terrifying incident,” said Gilles Poux, mayor of La Courneuve. “All I hope is that it wasn’t the father who threw him out of the window.”
The man is now in police custody.