A diesel engine having: a reentrant type cavity 11 depressed in the top of a piston 4; fuel injection means 9 that injects fuel towards the cavity 11; exhaust gas recirculation means 19 that recirculates a part of the exhaust gas into a combustion chamber; and a control device 26 that controls the fuel injection timing by the fuel injection means 9 and the EGR ratio or EGR quantity by the exhaust gas recirculation means 19, wherein in a predetermined operating region, the control device 26 implements premixed combustion by controlling the fuel injection timing by the fuel injection means 9 so that fuel injection is completed before the compression top dead center of the piston 4 and so that all the injected fuel enters the cavity 11, as well as controlling the EGR ratio or the EGR quantity by the exhaust gas recirculation means 19 so that the fuel injected by the fuel injection means 9 is ignited near the compression top dead center of the piston 4 after injection of fuel is completed. In this way, favorable premixed combustion can be implemented, and favorable combustion can be ensured even when the combustion is switched to diffuse combustion.