The migrant from Iraq was killed on Friday after he was hit by a train in Loon-Plage in the Nord department, reported BFM TV.
Another two migrants were also hit by the train, although they both survived.
One was taken to a hospital in Dunkirk in a state of shock, while the other was treated for hip injuries.
The ages and identities of the trio remain unknown.
The migrants were hit at a railway not far from the Grande-Synthe camp, which acts as a temporary home to around 700 mostly Kurdish refugees.
In nearby Calais, 14 migrants have been killed so far this year in attempts to get to the UK, most often in accidents on motorways.
An Eritrean died on Sunday after being hit by a car on a motorway near the port city.
Migrants desperate to get to Britain regularly try to stow away on lorries heading to the Channel ports for the crossing to England.