PURPOSE: To improve the sealing property at the abutting surface between a fixed scroll and the end plate of an oscillating scroll, and to suppress a friction following the rotation of both scrolls at the minimum, so as to reduce a gas leakage, by providing a labyrinth seal at least at one side of the opposite sliding surfaces of the oscillating scroll and the fixed scroll.

CONSTITUTION: At both sliding surfaces 33 and 34 of a fixed scroll 6 and an oscillating scroll 7, a labyrinth seal 35 along the full periphery is provided to the sliding surface 33 of the end plate 11 of the oscillating scroll 7. As a result, a gas pressure of a high pressure or a medium pressure flowing in from a back pressure chamber 39 into a compression chamber 14 generates a pressure loss by plural circular grooves to form the expansion chamber of the labyrinth seal 35, and the gas pressures at the engaging part of laps 10 and 12, and in the back pressure chamber 39 can be balanced. Consequently, the gas flowing in from the back pressure chamber 39 into the compression chamber 14 is reduced along the full peripheries of the scrolls 6 and 7, and the performance of a fluid machine can be improved.