PURPOSE: To enable multistage capacity to be varied without using any inverter circuit by providing a small capacity rotary type second compressor section together with a large capacity rotary type first compressor section having a release means to combine these sections for running.

CONSTITUTION: A rotary compressor 1 is constructed to provide a large capacity first compressor section 4 and a small capacity second compressor section 5 in series. In respective intake pipes 4a, 4b of rotary compressor 1 are interposed change-over valves 25, 26. A combined portion of intake pipes 4a, 5b is connected to a four-way valve 27 together with a discharge pipe 18 and constructed to individually compress or discharge in parallel fluid by the opening and closing motion of respective change-over valves 25, 26. Also, a release circuit 29 is provided between a release port 20 and the upstream section of intake pipes 4a, 4b.