Abstract: A fuel injection control device of a diesel engine is provided. The device includes an engine body, a fuel injection valve, a turbocharger, a low-pressure EGR system, and a controller for operating the engine body. Within a predetermined high engine-load operating range, the controller controls the fuel injection valve to operate the low-pressure EGR system and perform main and post injections. Within the operating range where the post injection is performed, when the engine load is lower than a predetermined load, an injection amount of the post injection is set to a first injection amount and an injection timing of the post injection is set to a first timing, and when the engine load is higher than the predetermined load, the injection amount of the post injection is set to a second injection amount and the injection timing of the post injection is set to a second timing.