A diesel engine comprising: a fuel injection apparatus for injecting a fuel into a combustion chamber; an external EGR (exhaust gas recirculation) apparatus for returning part of exhaust gas present in an exhaust channel into an intake channel via an EGR channel; an internal EGR apparatus for controlling opening-closing timing of an intake valve or exhaust valve and returning part of the exhaust gas into the combustion chamber or retaining it therein; and a control apparatus for controlling the fuel injection apparatus, the external EGR apparatus, and the internal EGR apparatus; such that the control apparatus implements in a prescribed operation region a premixed combustion in which the fuel is injected before the compression top dead center of a piston, the EGR of a comparatively large quantity is implemented, and the mixture ignites after the end of fuel injection, and implements outside the prescribed operation region a normal combustion in which the fuel is injected in the vicinity of the top dead center, the EGR is implemented in a quantity less than that when the premixed combustion is implemented, and the fuel ignites during this injection; and the control apparatus controls the EGR ratio by using both the external EGR apparatus and the internal EGR apparatus when the premixed combustion is implemented, and controls the EGR ratio by using only the external EGR apparatus, without implementing the EGR with the internal EGR apparatus, when the normal combustion is implemented, characterized in that when implementing the premixed combustion, the control apparatus controls the external EGR apparatus so that the EGR ratio produced by the external EGR apparatus becomes substantially equal to the maximum EGR ratio attained when the normal combustion is implemented and controls the internal EGR apparatus so as to compensate the insufficiency in the EGR produced by the external EGR apparatus. a fuel injection apparatus for injecting a fuel into a combustion chamber; an external EGR (exhaust gas recirculation) apparatus for returning part of exhaust gas present in an exhaust channel into an intake channel via an EGR channel; an internal EGR apparatus for controlling opening-closing timing of an intake valve or exhaust valve and returning part of the exhaust gas into the combustion chamber or retaining it therein; and a control apparatus for controlling the fuel injection apparatus, the external EGR apparatus, and the internal EGR apparatus; such that the control apparatus implements in a prescribed operation region a premixed combustion in which the fuel is injected before the compression top dead center of a piston, the EGR of a comparatively large quantity is implemented, and the mixture ignites after the end of fuel injection, and implements outside the prescribed operation region a normal combustion in which the fuel is injected in the vicinity of the top dead center, the EGR is implemented in a quantity less than that when the premixed combustion is implemented, and the fuel ignites during this injection; and the control apparatus controls the EGR ratio by using both the external EGR apparatus and the internal EGR apparatus when the premixed combustion is implemented, and controls the EGR ratio by using only the external EGR apparatus, without implementing the EGR with the internal EGR apparatus, when the normal combustion is implemented, characterized in that when implementing the premixed combustion, the control apparatus controls the external EGR apparatus so that the EGR ratio produced by the external EGR apparatus becomes substantially equal to the maximum EGR ratio attained when the normal combustion is implemented and controls the internal EGR apparatus so as to compensate the insufficiency in the EGR produced by the external EGR apparatus.