Positive displacement compressor

The present invention provides a positive displacement compressor which does not relates to a pressure difference between a discharging pressure of working fluid and a pressure of oil storing part of the positive displacement compressor, and can realize miniaturization of an oil returning device. The positive displacement compressor of the invention comprises the following components: an oil return chamber (95) which stores the separated oil that is separated from the stored working fluid, a floater for floating the separated oil stored in the oil return chamber, and a floater valve body (70ab) which is composed of the floater valve part and is interlocked with the vertical floating of the floater for opening and closing a communicating opening (downstream side oil return passage opening (80y1)) communicated with the oil storing part, wherein the communicating opening of the oil storing part is formed at the side wall surface of a cylindrical floater valve opening (70c) formed at the base of the oil return chamber. The floater valve part is formed with a move of moving along the side wall surface of the floater valve opening for opening and closing the communicating opening. The lower space of the floater valve, which is opposite with the lower end surface of the floater valve part, is communicated with an oil return chamber pressure-equalizing passage (70d). Through the ascending of the floater, the separated oil storing chamber of the oil return chamber and the communicating opening are communicated by a upstream side oil return passage 80x.