PURPOSE: To prevent the occurrence of wear in a metal end face in case of adopting a copper alloy metal as well as to aim at improvement in its durability, by installing a platelike washer interposingly between a radial metal housed in a bearing box of a supercharger and a circlip supporting this radial metal.

CONSTITUTION: In order to stabilize its rotation in a radial direction, a supercharger having an ultrahigh speed turbine and a compressor is provided with a radial metal 6 inside a bearing box 5 and supported by a circlip 7, while a platelike washer 30 is interposingly installed in position between the radial metal 6 and the circlip 7. And, a lubricating oil film is secured in space between the radial metal 6 and the platelike washer 30 and thereby no wear is made so as to be produced at a metal end face even when the radial metal 6 is forcibly pressed to a thrust direction. With this constitution, such a copper alloy as being weak against mechanical cutting in spite of excellence in black and corrosion resistance capacity is adoptable for the radial metal 6, thus durability in the supercharger is yet more improvable.