A driving force transmission device transmits driving force between an outer case made of magnetic substance and inner shaft. A main clutch mechanism, an electromagnetic type pilot clutch mechanism and cam mechanism are arranged between the outer case and inner shaft. The main clutch mechanism transmits driving force between the outer case and inner shaft. The pilot clutch mechanism controls operation of the main clutch mechanism and comprises an electromagnet, an armature and a friction clutch. The cam mechanism amplifies output of the pilot clutch mechanism and transmits amplified output to the main clutch mechanism. The driving force transmission device further comprises a first regulation member and/or a second regulating member. The first regulating member adjusts a clearance between the cam mechanism and the armature to be more than a predetermined distance. The second regulating member adjusts an axial position of the friction clutch.