To provide the joint part structure of a propeller shaft of simple constitution that can suppress the transmission of vibration on the engine side.

A coupling body 5A with an elastic member 30 is interposed between an input shaft side flange 26 and 3 propeller shaft 3. A support member body 31a of a support member 31 fittingly insert the elastic member 30. The elastic member 30 absorbs vibration transmitted from one of the input shaft side flange 26 and propeller shaft 3 to the other so as to be able to reduce the transmission of torsional vibration and to attain frequency movement of torsional resonance. In addition, the gear sound of a diffrential gear 1 can be reduced. Since the elastic member 30 is covered with the support member 31 to prevent stones, water, and the like from coming in contact with the elastic member 30, the durability of the elastic member 30 can be improved.