Abstract: A rotary compressor, more particularly, a positive cam type compressor wherein a movable isolator plate is driven by a positive cam. The positive cam has a helically twisted disk portion, and is fitted in a cylinder slidably. The cylinder cavity is divided into operating compartments in which suction and compression processes are performed alternately, when the positive cam is rotated by a driver shaft. The positive cam and the isolator plate form a sliding pair, so that the plate can be reciprocatively moved when the cam rotates. The circulation of lubricating oil is positively effected by the reciprocating motion of the isolator plate.Thus, there can be provided a considerably small and light compressor that is constructed with relatively smaller number of parts. Furthermore, the compressor of the present invention may have good characteristics of vibration and noise. The above compressor is suitable to an air conditioner for vehicle.