PURPOSE: To improve reliability of fluid supplying operation, by avoiding frequent repetition of starting and stopping of a pump through employment of such an arrangement that fluid pressure is not applied to a pressure switch when the flow rate of fluid has exceeded a prescribed value but fluid pressure is detected by the pressure switch when the flow rate of fluid has become lower than a prescribed value.

CONSTITUTION: When pressure of fluid in a fluid passage is lowered to a prescribed lower limit value of a pressure switch 13, the switch 13 is turned ON and a motor 12 is set into operation, so that fluid is discharged from a pump 11 via a connecting pipe 24. As the fluid passes through an orifice 20, the differential pressure on the opposite sides of the orifice 20 is transmitted to a low-pressure chamber 28 via a pressure transmitting passage 40, thus imparting the pressure difference between the low-pressure chamber 28 and a high-pressure chamber 27. This pressure difference is acted to a resilient member 29 and closes a pressure controlled valve 23. Therefore, when the valve 23 is closed, the pressure switch 13 is kept at the pressure acted just before closing of the valve 23, so that fluid can be supplied in a stable manner without influence of fluid pressure developed when the pump 11 is operated.