A control device for a diesel engine, the device comprising: a supercharger (61, 62): a fuel-injector; an accelerator opening detector that detects a degree of opening of an accelerator pedal; and an actual supercharging pressure detector that detects an actual supercharging pressure, wherein controlling an injection mode of the fuel-injector allows main injection that is started near a compression top dead center and pilot injection that is executed prior to the main injection to be performed depending on an operating state of the diesel engine, and cylinder pressure control is performed if the degree of opening of the accelerator pedal decreases during operation of the supercharger (61, 62) and an actual supercharging pressure detected with the actual supercharging pressure detector is equal to or higher than a predetermined value, the cylinder pressure control allowing an interval between a start timing of the pilot injection and a start timing of the main injection to be broader, wherein the interval is broader than during regular control that is executed if the actual supercharging pressure is less than the predetermined value, wherein in the cylinder pressure control, the interval is broadened by retarding the start timing of the main injection as compared to if the actual supercharging pressure is less than the predetermined value, characterised in that the cylinder pressure control is not executed even if the actual supercharging pressure is equal to or higher than the predetermined value, in a case where the degree of opening of the accelerator pedal decreases during operation of the supercharger, and a fuel injection amount in the pilot injection is less than a predetermined amount. a fuel-injector; an accelerator opening detector that detects a degree of opening of an accelerator pedal; and an actual supercharging pressure detector that detects an actual supercharging pressure, wherein controlling an injection mode of the fuel-injector allows main injection that is started near a compression top dead center and pilot injection that is executed prior to the main injection to be performed depending on an operating state of the diesel engine, and cylinder pressure control is performed if the degree of opening of the accelerator pedal decreases during operation of the supercharger (61, 62) and an actual supercharging pressure detected with the actual supercharging pressure detector is equal to or higher than a predetermined value, the cylinder pressure control allowing an interval between a start timing of the pilot injection and a start timing of the main injection to be broader, wherein the interval is broader than during regular control that is executed if the actual supercharging pressure is less than the predetermined value, wherein in the cylinder pressure control, the interval is broadened by retarding the start timing of the main injection as compared to if the actual supercharging pressure is less than the predetermined value, characterised in that the cylinder pressure control is not executed even if the actual supercharging pressure is equal to or higher than the predetermined value, in a case where the degree of opening of the accelerator pedal decreases during operation of the supercharger, and a fuel injection amount in the pilot injection is less than a predetermined amount.