Officials said the damage was discovered in the French city on Saturday morning.
Strasbourg mayor Roland Ries said it was “a new antisemitic act” adding the stone "must weigh 300 or 400 kilograms."
Mr Ries said. "It wasn't pushed off by a single individual."
Writing on Facebook after visiting the memorial on Saturday, Mr Ries said: “I say once again: Enough!"
It comes following a spate of antisemitic acts in France in recent months.
Last month, 80 Jewish gravestones were spray-painted with swastikas in a Jewish cemetery close to Strasbourg.
The Jewish graves were vandalised in a small Alsace town.
Photographs from the scene showed swastikas and antisemitic graffiti daubed on tomb stones.
