A fuel supply device includes a low-pressure fuel pump, a high-pressure fuel pump, an accumulator for accumulating the pressurized fuel, fuel injection valves, a relief valve for restricting an upper limit value of a fuel pressure in the accumulator, a high-pressure fuel pressure sensor, and a control unit for setting a target fuel injection pressure, controlling the high-pressure fuel pump so that the fuel pressure in the accumulator reaches the target fuel injection pressure, and regarding the present target fuel injection pressure as a detection value of the high-pressure fuel pressure sensor and setting the high-pressure fuel pump in an operational state with a maximum discharge amount or a non-operational state when detecting an abnormality of the high-pressure fuel pressure sensor.This enables the fuel to be injected with an appropriate injection pulse width corresponding to an actual fuel pressure even if the high-pressure fuel pressure sensor experiences disconnection.