"About 60 people from Germany have died or killed themselves, at least nine in suicide attacks," Hans-George Maassen told the Welt am Sonntag newspaper.
"That's a sad success for Islamist propaganda."
In all about 550 German nationals have joined the IS in the conflict zone, and of these 180 have returned to Germany, he said.
In mid-October, Germany announced new measures to prevent its citizens from travelling to join the jihadist cause in Iraq and Syria, including confiscating their identity papers.