A compressor body is formed such that a compression chamber is divided by a rotor, a cylinder, side blocks and vanes, a housing which covers the compressor body is included, and an outline shape of a cross section of an inner circumferential surface of the cylinder is formed such that, in a period of one rotation of the rotor, (i) a region in which a capacity of the compression chamber increases, (ii) a region in which the capacity of the compression chamber reduces, (iii) a region in which a capacity reduction rate of the compression chamber is smaller than a capacity reduction rate of the region (ii), and (iv) a region in which the capacity reduction rate of the compression chamber is larger than a capacity reduction rate of the region (iii) are consecutively provided in order.