To provide an oil seal device of a supercharger capable of surely preventing lubricating oil from leaking to the outside of the supercharger in the wide operating range of an engine.

In this supercharger 1, a turbine 12 is rotated by the gas flow of exhaust gas to rotate a compressor 13 installed on a rotating shaft for the turbine so as to compress and feed suction air. Labyrinth fins 26 are fitted to a bearing support 22 positioned around the rotating shaft so that the lubricating oil fed to the bearings 8a, 8b, 9, and 10 of the rotating shaft 11 does not leak to the outside of the supercharger. Fins 28 capable of spattering the lubricating oil leaking along the surface of the rotating shaft to the outside by a centrifugal force by the rotation of the rotating shaft are formed integrally with the outer periphery of a sleeve 16 on the rotating shaft positioned on the inside of the labyrinth fins.