A piston compressor may prevent excessive oil from accumulating in a crank chamber while securing the supply of oil to a swash plate. In a piston compressor in which an oil separation passage is formed in a shaft and a crank chamber communicates with a suction chamber through the oil separation passage, a supply passage opens at a region of a cylinder block opposed to a swash plate to allow a working fluid introduced from a discharge chamber into the crank chamber to be supplied to the swash plate and a bypass passage allowing the crank chamber to constantly communicate with the suction chamber is provided to prevent the accumulation of excessive oil in the crank chamber regardless of the operation condition. The bypass passage communicates with the crank chamber at a region positioned in the outer side of a rotation trajectory of the swash plate in the radial direction.