To suppress the vibration when a brake is applied and prevent a contact sound and the damage by shock force by providing an integrally molded rubber film at the contact section of a collar with an armature.

When no current is fed to an exciting coil 2, a disk 5 is pressed to a side plate 7 via an armature 4 by the pressing force of multiple coil springs 10 stored in a field core 1. The disk 5 generates torque by the frictional force on the contact faces of the armature 4 and the side plate 7 as the brake state. When a brake is applied, the armature 4 is moved in the peripheral direction to generate a contact sound, and a collar 8 might be damaged and deformed by strong shock force. A collar 21 provided with an integrally molded rubber film 21A on the inner and outer peripheral faces is employed in place of the conventional collar 8. The contact sound and strong shock force can be suppressed by the damping effect of rubber when a brake is applied.