PURPOSE: To perform the feed of oil to a bearing in any pressure ratio by communicating a back pressure chamber to a discharge port for oil through which oil is fed to a bearing by means of a differentral pressure by using a delivery pressure serving as a high pressure source and not communicating it to any place except the discharge port.

CONSTITUTION: A back pressure chamber 11 is provided in a state to be closed by a seal part 3b sealed through contact between the under surface of the outer periphery of the end plate 3a of a revolving scroll 3 and the seat surface of a frame 4. Oil fed by means of a differential pressure with a delivery pressure serving as a high pressure source and after a feed to a bearing is caused to flow therein, and a part of a refrigerant dissolved in the oil is gasified to increase a pressure. When a load by a pressure in the back pressure chamber 11 is balanced with a load from the compression chamber 9 side, the revolving scroll 3 is lifted and oil and refrigerant gas are escaped in a low pressure space at the outside of the seal part 3b. A back pressure being neither increased nor decreased but balanced, the revolving scroll 3 supports a fluid force. This constitution effects the feed of oil by a differential pressure in any condition and eliminates an constrain on a pressure ratio as an operation condition.