The body was found in a stream near the campsite at Saint-Julien-de-Peyrolas on Monday evening.
It has been taken for an autopsy and identification.
The man was reported missing on 9 August after the site was evacuated because of flooding that wrecked tents, caravans and amenities.
The site was run by a German organisation, Jugerdförderung Saint-Antonius, but did not have the necessary permission from local authorities.
At the time of the storm that caused the floods there were 138 children and 46 adults staying there.
Two German nationals, the president and vice-president of the organisation, have been charged with causing injuries and endangering lives, as well as camping without a permit.