To improve a method for measuring fuel so as to prolong the life of a measuring device by arranging the measuring device between a fuel high pressure pump and a fuel high pressure storage with and cutting off fuel supply for interrupting measurement.

Fuel made into high injection pressure by a fuel high pressure pump 4 is supplied to a fuel high pressure storage with 1. Fuel injection via a fuel injection valve 10 is electrically controlled via a control line 11. A control device 14 also controls the running of the fuel high pressure pump 4 according to the fuel pressure to the fuel high pressure storage with 1. For detecting the individual injection amount of the injection valve 10, a measuring device 17 is provided. The measuring operation of the measuring device 17 is controlled by the control device 14 and an operation is connected/disconnected. The measuring device 17 has a measuring cylinder 19. A measuring piston 20 is arranged in the measuring cylinder 19 so as to be slidable. During standard running, the measuring device is cut off. Thus, the life of the measuring device is greatly prolonged.