PURPOSE: To monitor the fuel injection state with high precision by comparing the pressure in a delivery pipe and a standard pressure memorized in a memory means and outputting the result of the comparison.

CONSTITUTION: A pressure adjusting valve 16 is installed into a delivery pipe 2, and the pressure signal supplied from a pressure sensor 48 is input into an ECU 38. A certain standard pressure value memorized into the ROM 56 of the ECU 38 is compared with a detected pressure value. When it is judged that the detected pressure is higher than the standard pressure, an anomaly signal Es for lighting up a warning lamp 60 is outputted, and a discrimination signal for discriminating the anomaly due to the injection of an injector 30 is prepared.