To control or prevent sucking of oil to be supplied to radial bearings 31 and 32, in a supercharger 20 where a rotary shaft 25 being provided with a turbine wheel 22 and a compressor impeller 24 is freely and rotatably supported by the radial bearings 31 and 32.

The supercharger includes: an oil supply device 50 for supplying oil to the radial bearings 31 and 32; and a control device 100 which controls an oil supply pressure caused by the oil supply device 50. The control device 100 checks whether a condition that it is going to be more likely that oil to be supplied to the radial bearings 31 and 32 is sucked by a turbine housing 21 or a compressor housing 23 is met. When determining that the condition is met, the control device sets the oil supply pressure lower than when the condition is not met.