Samuel Mouchard of the housing charity Fondation Abbe Pierre said the man, identified only as Dominique, 50, paid $439 per month to stay in the tiny apartment, The Local.fr reported Friday.
"It is scandalous," Mouchard said.
Mouchard said tiny apartments are becoming an increasing problem in the Paris.
"Landlords are profiting from the housing crisis in Paris," Mouchard said. "Many people don't have a choice but to accept to live in these tiny apartments because they fear being out on the street."
Mouchard said the landlords are flouting laws requiring apartments to have at least 96.8 square feet of livable space.
"Some landlords are unscrupulous. The law is there but it needs to be enforced," he said. "Tenants need to know that it's forbidden. If they have doubts they can go to their local Town Hall where measures can be taken to protect them or to rehouse them."