PURPOSE: To prevent a change in a fuel injection quantity due to a change of cylinder internal pressure, by arranging such that a fuel injecting pressure is corrected in response to the internal pressure of cylinder for a diesel engine as measured.

CONSTITUTION: The cylinder 1 of Diesel engine GE is provided with a pressure sensor PT. Data pertaining to the cylinder internal pressure as detected is transferred to a pressure correcting device 3 at the time of fuel injection being started with a hydraulic control valve CV being rendered operable via a gate 6. An injecting pressure instructive value outputted by an injecting pressure pattern generator 5 has its cylinder internal pressure value only calculated by an adding device. The injecting pressure instructive value as corrected is outputted to a hydraulic control device 2. The fuel pressure of hydraulic pump PM is adjusted to match the instructive value, and the injection of fuel is carried out by a hydraulic control valve CV through an injection nozzle NZ at a predetermined timing. In this manner, the fuel injecting quantity can be adjusted no matter what changes may take place in the cylinder internal pressure.