To rapidly recognize an operation failure side when the operation failure occurs in one of two pressure regulating valves, in case the two pressure regulating valves are disposed and a redundancy mechanism where the operation failure in one valve is compensated by the other valve is provided.

A fuel injection device has first and second pressure regulating valves 20 and 21 as a pressure regulating means 4 of a fuel injection circuit, and the respective regulating valves are connected to a circulation passage 3 communicating with a fuel injection passage 2 and a bypass passage 29 via first and second orifices 22 and 27. The fuel injection device has first and second sensors 24 and 28 for individually detecting fuel pressure applied to each pressure regulating valve. A control unit 31 of a failure diagnosing means 30 compares respective fuel pressures P1 and P2 detected by the first and second sensors 24 and 28 with a preset fuel pressure P of the fuel injection passage 2. When P1 equals to P2, the control unit 31 determines the first and second orifices 20 and 21 are normal. When an operation failure occurs in one valve, P1 and P2 change. Therefore, the control unit determines abnormality based on the pressure difference, and a display unit 33 announces the abnormality occurrence and the place where abnormality occurs.