To prevent response delay and to damp torsional vibration transmitted to a power transmission route. A vibration damper includes a first route R1 provided with a coil spring 43 as an elastic member, and a second route R2 provided with a sun gear 5s as an inertial body formed to be parallel as power transmission routes between an engine 10 to a transmission 20, and by switching the first route R1 and the second route R2 by a first clutch C1 and a second clutch C2, switchover to a state in which an inertial torque acts on the power transmission route by the sun gear 5s and a state in which the inertial torque is not generated is carried out.