A natural refrigerant low-pressure shell-type rotary compressor in which the amount of oil contained on the high-pressure side is reduced with sufficient lubrication and sealing performance at a sliding section secured. The compressor has a rotary refrigerant compression mechanism provided in a low-pressure enclosed container and having vanes, an oil separation element for separating lubricating oil from the refrigerant, and an oil supply passage for supplying the separated lubricating oil to a vane back pressure chamber of the compression mechanism, a crankshaft, a bearing, a cylinder, a piston, and oil supply spaces between the vanes. Vane skip is suppressed, and efficient lubrication and high sealing performance at the sliding section and a reduction in the amount of the oil contained on the high-pressure side are achieved at the same time. The compressor is highly reliable, is of low cost, has high performance, and uses a reduced amount of refrigerant.