To shorten the dimension in the axial direction of a power transmitting device.

A pulley 1 is supported by the cylindrical projected part A of a compressor so as to be freely rotated. And hub assemblies 3 are mounted on the rotating shaft of the compressor. Plural mounting holes 5a and plural escape holes 5b are formed in the holding member 5 of the hub assemblies 3. An elastic member 6 is fixed to the holding member 5 by letting each projection with a flange 6a be press fitted and fitted in the respective mounting holes 5a. Plural recessed parts 6b are formed in the elastic member 6, and the fitting of each recessed part 6 with each projected part 1f of the pullet 1 thereby allows the pulley 1 to be connected with the hub assemblies 3. When a rotary shaft B is locked, each projected part 1f of the pulley 1 rides over the recessed parts 6b of the elastic member 6, and concurrently, the projected part 6c of the elastic member is elastically deformed into the escape holes 5b of the holding member 5.