PURPOSE: To provide a necessary sufficient vibration reducing effect over a wide range by mounting a mass member through an auxiliary elastic body on a propeller shaft having both ends coupled with a mating side rotary member through a rubber system elastic body.

CONSTITUTION: A ring-like mass member 7 is coupled integrally with the outer peripheral of the central portion of a propeller shaft 1 through a rubber system auxiliary elastic body 6. The weight of the mass member 7 and the spring constant of the auxiliary elastic body 6 are respectively set such that the natural frequency of the auxiliary vibration system determined by the auxiliary elastic body 6 functioning as a spring and the mass member 7 coincides with the natural frequency of a main vibration system having the propeller shaft 1 itself as a mass and the rubber system elastic bodies 2, 4 as springs. Thus, when the natural frequency of the auxiliary vibration system for example is set to the characteristic value of bending vibration of the main vibration system, a peak of torque transmission rate appears before and after the resonance frequency, while the peak value itself is lower than prior one and the transmission rate is substantially lower than prior one near the resonance frequency so that a vibration reducing effect can be obtained in a wider region.