PURPOSE: To prevent side surfaces from being abnormally worn, and also to restrain consumption power from being increased by maintaining airtightness through a process of pressing the side surface of a spiral lap of a turning scroll to the side surface of a spiral lap of a fixed scroll in low-speed operating, and by maintaining a clearance between the side surfaces of the spiral laps in high-speed operating in which the rotational number is the specific rotational number or more.

CONSTITUTION: A weight 10 for generating centrifugal force Fs to act on a turning scroll 2 and centrifugal force Fc smaller than it in the revolution turning of the turning scroll 2 is provided on a drive bush 5. And an elastic bouncing member 15 is provided for energizing the drive bush 5 along the slide direction in the direction 6 that the revolution turning radius is increased. Thereby, the turning scroll 2 is displaced in the direction that the revolution turning radius is decreased when the revolution turning speed is the specific value or more.