Abstract: In a screw compressor, on a bearing side relative to a discharge port of a compression chamber in a casing, an intermediate-pressure chamber to which an intermediate-pressure coolant is supplied from outside of the casing is provided in a high-pressure space surrounded by an outer cylinder and an intermediate cylinder of the casing and communicating with the discharge port, and the intermediate-pressure coolant has a temperature and a pressure that are lower than those of a coolant in the high-pressure space and higher than a coolant in a low-pressure space on a motor side relative to the discharge port in the casing. The intermediate-pressure chamber and the low-pressure space communicate with each other.