PURPOSE: To supply oil of constantly stable back pressure to the backside of vanes without any deterioration of the capacity of a captioned compressor by providing a throttle constructed of sintered alloy or metal filter in an oil passage to conduct the oil under a discharge pressure tothe backside of vanes.

CONSTITUTION: A filter 32 constructed of sintered alloy or metal filter is inserted into an oil-feed hole 31 connected to the back space of vanes 15 in an R plate 4. The oil under a discharge pressure is reduced in its pressure by the resistance of the flow passage of this filter 32, and the oil of a proper pressure is supplied to the backside of vanes 15. This construction permits to supply the oil of constantly stable back pressure to the backside of vanes. That is, since the surface area of the filter 32 is much greater than a single throttling hole or the like, this part is free from choking. Meanwhile, since dust or the like can be filtered by the filter 32, vanes 15 and others can be prevented from damages for obtaining a long life of a compressor.