<p>A screw compressor (1) is provided with a screw rotor (30) and a compression mechanism (20) having a gate rotor (40), within a casing (10). The casing (10) has a low-pressure chamber (12) through which a low-pressure refrigerant introduced to the compression mechanism (20) passes, and a high-pressure chamber (11) through which a refrigerant compressed by the compression chamber (20) passes. A bypass mechanism (50) is provided with an internal bypass passage (52) which connects the high-pressure chamber (11) to the low-pressure chamber (12), and an inner valve (53).</p>
