The present invention concerns an diesel engine fuel injection control, and a regeneration control method of exhaust gas post-treatment apparatus using this fuel injection control, and the engine fuel injection control for performing after injections (Fas, Fam) after a main injection (Fm) for activation and regeneration of the exhaust gas post-treatment apparatus, through the rising of diesel engine exhaust gas temperature or the decrease of the oxygen concentration in the exhaust gas, is composed to perform the after injections (Fas, Fam) in a range of 40° ATDC to 90° ATDC of the crank angle.Whereby, the main injection can be burned, without misfire, even when the main injection is largely retarded, or, the injection quantity is increased / decreased, and the engine operation can be sustained, by keeping the engine combustion in a good state.