A compression mechanism units include cylinder chambers into which a low-pressure gas is introduced, vanes contained in a vane groove, and a spring body that always causes compression operation in the cylinder chambers by providing an elastic force to a rear-end portion of one of the vanes, includes a pressure switching mechanism that switches to perform compression operation by guiding a high-pressure gas/not to perform the compression operation by guiding a low-pressure gas, is provided with a lubricating oil communication path communicatively connecting a oiling groove and a oil stagnant portion, and opposing the oiling groove to a portion other than the lubricating oil communication path when the vanes are in a top dead center position.