A vane compressor includes a cylinder block, a cylinder chamber having an ellipsoidal inner wall, a rotor whose outer circumferential surface is provided with vane slots formed thereon, a drive source for the rotor, and vanes housed in the vane slots, respectively. The rotor is rotated by the drive source while the vanes are protruded from the vane slots by backpressure generated in backpressure spaces in the vane slots to contact end edges of the vanes with the inner wall of the cylinder chamber. The compressor further comprises a stop mechanism that makes the rotor stopped at a predetermined rotational position where a difference between a total volume of the backpressure spaces when operated and a total volume of the backpressure spaces when stopped becomes minimum. According to the compressor, chattering can be prevented without extra workings on the vanes or the rotor and without providing extra parts.