Piston type compressor having arcuately shaped fluid port

1. Field of the Invention A suction port as a fluid port of a piston type compressor is contoured with reference to a middle line passing through a middle point of a maximum length of the suction port in the longitudinal direction of the suction valve and perpendicularly crossing a reference line extending in the longitudinal direction. The middle line divides the suction port into a first section positioned on the proximal end side and a second section positioned on the distal end side. An area of the second section is greater than an area of the first section. A width increasing region is disposed in which the width of the suction port becomes gradually greater from the proximal end side to the distal end side, and the length of the width increasing region occupies a major part of the maximum length of the suction port.