PURPOSE: To diagnose both electrical trouble and abnormality caused by mechanical trouble and the like, of an electromagnetic valve, and correctly diagnose those abnormalities according to the behavior of actual fuel injection.

CONSTITUTION: A fuel quantity pressure-fed to a fuel injection nozzle 4 is controlled by controlling an electromagnetic spill valve 23 in a fuel injection pump 1. A pressure sensor 47 for detecting fuel pressure is provided on the fuel injection nozzle 4. An injection ending time is judged by an ECU 71 based on the state of variation of the detected fuel pressure. Difference between an injection ending set time and the injection ending time of the controlled electromagnetic spill valve 23 is calculated in the ECU 71, and the fuel injection pump 1 is judged as abnormal when the difference is larger than a specified delay time. The injection ending time judged from the state of variation of the fuel pressure is largely changed when electromagnetic spill valve 23 is not operated as required by some reason, and the abnormality caused by various kinds of trouble of the electromagnetic spill valve 23 is diagnosed based on the variation.