To stabilize a damper characteristic by reducing the diameter in each of both end parts of an inside spring smaller than that of the center part, when the inside spring whose length is shorter than that of an outside spring is inserted into the outside spring.

In an inside spring 32X, a diameter of the small diameter part in each of both end parts is gradually reduced in several pitches as against the large diameter part in the center. On the inside of an outer circumference flange 28 of a piston 22, an outside spring 32Y is held circularly by means of a retainer plate. The winding direction of the inside spring 32X, whose length is shorter than that of the outside spring 32Y, is opposite to that of the outside spring 32Y, and the inside spring 32X is inserted into the outside spring 32Y movably. Torsional torque from the piston 22 is transmitted to the retainer plate 23, the outside spring 32Y, and a driven plate 31 sequently. In this process, a coil diameter in each of the both end parts of the inside spring 32X is smaller than the coil diameter of the center part, so that the end parts of the inside spring 32X are prevented from climbing over the outside spring 32Y.