A compressor including a motor having a rotary shaft, a rotor and a stator, and an impeller at a front end of the rotary shaft to suction refrigerant in an axial direction and compress the refrigerant in a centrifugal direction. The compressor has a collar at a rear end of the rotary shaft and coupled to the rotary shaft to be extended outwardly in a radial direction of the rotary shaft. Radial bearings support a radial movement of the rotary shaft at a front and rear of the stator. A thrust bearing prevents an axial movement of the rotary shaft. A mechanical backup bearing also prevents the axial movement of the rotary shaft. A fixing unit supports the backup bearing at the rear end of the rotary shaft, wherein the backup bearing is arranged to overlap the thrust bearing in the radial direction of the rotary shaft.