In a swash-plate compressor, pistons are slidably received in cylinder bores. A drive shaft is extended through a crank chamber, and is rotated through an electromagnetic clutch means associated therewith. A conversion mechanism is provided on the shaft for converting a rotational movement of the shaft into a reciprocation of each piston in the corresponding cylinder bore such that a suction stroke and a discharge stroke are alternately executed therein. A fluid is introduced from a suction chamber into the bore during the suction stroke, and during the compression stroke, the fluid is compressed in and discharged from the bore into a discharge chamber. The conversion mechanism is constituted such that a stroke length is shortened in response to an increase of a pressure in the crank chamber, and vice versa. A first passage communicates the crank with the suction chamber, and a second passage communicates the crank chamber with the discharge chamber. A control valve is provided in one of the first or second passage, and is magnetically actuated by the clutch for controlling the pressure in the crank chamber such that the piston stroke can be minimized whenever the clutch is electrically deenergized.