An airtight damper, an input axis, and a flywheel are mounted to the input axis with a bolt. A torque transmitter, a torque transmitter attachment unit of the flywheel, and a support plate are united with each other using a bolt. The torque transmitter includes a spline unit. A pressure plate engaged with the spline unit is pressed by a pressure spring so as to press a friction plate and a torque transmitter plate against the support plate. Since the torque transmitter plate is fixed to a drive plate by a rivet, the torque from the input axis can be transmitted to the drive plate. Although the torque from the engine is larger than an allowable value, a friction member can slip at a constant torque depending on the pressure of the pressure spring, thereby protecting the damper against an excess load.