To provide a gas compressor in which cooling medium gas guided to a suction gas space always flows in a fixed direction.

This gas compressor is provided with a suction port 2 sucking gas from outside, the suction gas space 4 communicating to the suction port 2, a compressor main body 5, 6, 7, 11, 15 communicating to a suction gas space 4. A partition plate 25 as a straightener for making gas guided to the suction gas volume 4 always flow in the fixed direction and sucked to the compressor main body is provided in the suction gas space 4 in such a manner of partitioning the suction gas volume. Since suction pressure loss is inhibited by reducing resistance of a pathway of suction gas, and drop of density of gas sucked in the gas compressor part is inhibited by preventing heating of suction gas, performance of the gas compressor can be improved.