According to the present invention, a change-over means is provided between a mechanical oil pump and a clutch of an automatic transmission device for connecting an engine with the automatic transmission device, a first check valve is provided in a passage connecting the mechanical oil pump with the change-over means so that it allows the flow of working fluid discharged from the mechanical oil pump to the change-over means, and an electric oil pump is provided in parallel with the mechanical oil pump, wherein the electric oil pump is operated during an idling stop of the engine and an output side of the electric oil pump is connected to the passage between the first check valve and the change-over means so that the working fluid from the electric oil pump is supplied to the clutch of the automatic transmission device through the change-over means. Accordingly, the electric oil pump can be made smaller and the supply of the working fluid from the electric oil pump to the clutch can be surely prevented by the change-over means when the supply of the working fluid is not necessary.