PURPOSE: To prevent a fixed scroll from being deflected due to change in the pressure in a closed space at the time of driving a compression element, and to prevent the inner pressure of the closed space of the compression element from being higher than a predetermined level, even when the compression element is in a condition of liquid compression.

CONSTITUTION: A partition wall 6 that forms a discharge chamber S1 that is communicated with a discharge port 23, is provided on the discharging side of a compression element P provided with a fixed scroll 2 having the discharge port 23, and a moving scroll 3. A low pressure working chamber S4 communicated with the suction side of the compression element P, is provided between the partition wall 6 and the back surface side of the fixed scroll 2, while a relief path 8, the one end of which is opened to a closed space 4 of the compression element P, and the other end of which is opened to the low pressure working chamber S4, is provided on the fixed scroll 2, and a relief valve 9 is provided on the relief path 8.