To provide an oil relief mechanism easily securing a desired oil relief property, and to provide an oil relief device.

The oil relief mechanism M comprises a communication passage 25 communicating with a discharge passage, and a shaft-like valve element 70. A female screw 25a is formed on the inner peripheral face of the communication passage 25, and a male screw 70a is formed on the outer peripheral face of the valve element 70. The valve element 70 is fitted into the communication passage 25 in a forward/backward threaded manner with the male screw 70a threaded to the female screw 25a. A relief passage Ra is formed along a clearance between each of peaks 71a of a series of threads 71 of the male screw 70a and each of bottoms 23d of the female screw 25a, and a relief passage Rb is formed along a clearance between each of valley bottoms 71b of the series of threads 71 of the male screw 70a and each of peaks 25c of the female screw 25a.