PURPOSE: To enhance followability of a supercharger by driving a high pressure oil pump for press-supplying high pressure oil to an oil turbine wheel fixed to a connecting shaft of an exhaust turbosupercharger by the use of an electric motor controlled according to an engine operating condition.

CONSTITUTION: In an exhaust turbosupercharger SC attached to an engine E, an oil turbine wheel 6, which is driven by a high pressure oil, is fixed in the middle portion of a connecting shaft 4 for connecting an exhaust turbine wheel 1 to a supercharging compressor wheel 2. A high pressure pipeline 11 incorporating a high pressure oil pump P2 therein is branched from a pipeline 7 on a discharge side of an oil pump P1, which is driven by the engine E. The tip end of the high pressure pipeline 11 is connected to a nozzle for driving the oil turbine wheel 6. An electric motor M is connected to a drive shaft 12 of the high pressure oil pump P2, and is started or stopped by a controller 13 for inputting information such as an accelerating operation and an engine speed.