To provide a fuel supply device capable of detecting a failure condition of a flow passage shut off valve.

The fuel supply device 10 is provided with a fuel supply pipe 24 connected to a fuel pump 23, a fuel delivery pipe 25 connected to a downstream side of the fuel supply pipe 24 and a fuel return pipe 25 connected to a downstream side of the fuel delivery pipe 25. An injector 16 is connected to the fuel delivery pipe 25 and the floe passage shut off valve 40 is built in the fuel return pipe 26. The fuel supply pipe 24 and the fuel return pipe 26 are communicated via a bypass pipe 43 provided with a pressure control valve 44. The flow passage shut off valve 40 is controlled to open and close by a control unit 41 and the fuel return pipe 26 is switched to a communication state and a shut off state. It is determined based on a control state of the flow passage shut off valve 40 by the control unit 41 and a current value supplied to the fuel pump 23 whether the flow passage shut off valve 49 is in a failure condition or not.

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