PURPOSE: To make it possible to carry out various modes of operation with the control of a single control valve and as well to relieve shock upon starting, by disposing the control valve in the intermediate section of a coolant suction passage communicated with a compression chamber, and as well by piercing a coolant passage hole through a coolant passage and a rotor.

CONSTITUTION: A coolant passage is branched out into an upper suction passage 6 and a lower suction passage 7 at a branch point 5 downstream of a suction passage opening 4. A control valve 8 disposed at the branch point 5, is rotationally driven and positioned by a control motor 10 through a shaft seal device 9. With this arrangement upon starting the control valve 8 gradually rotates from its fully close position at suction passages 6, 7 so that shock upon starting is reduced. Further, upon fully open operation the control valve 8 opens the suction passages with no resistance so that operation may be made exhibiting its maximum capability. Further, upon control operation the supply amount of coolant is regulated in accordance with the rotation of the control valve 8 to carry out capacity control operation so that it is possible to carry out energy saving operation. Upon resting the control valve 8 rotates at once to the position where the suction passages are fully closed to prevent high pressure gas and oil from counterflowing toward the evaporator side, thereby heat loss upon restarting is prevented.