To stabilize a supercharger effect when load fluctuates and excellently control a load change.

This device is constituted to have an exhaust gas system in which a denitration device 36 is provided between an exhaust gas route from the exhaust part of a diesel engine 31 to the inlet of a supercharger 32, engine exhaust gas is distributed to the supercharger 32 and a supercharger bypass system 38 after engine exhaust gas is distributed to the denitration device 36 and a denitration bypass system 35 and is joined 37, subsequently, the outlet exhaust gas route 39b of the supercharger 32 and a supercharger bypass system 38 are joined 40 and exhaust gas is exhausted to a chimney etc., for instance. Based on a generated electric power command value 13 and other control command values, each of a normal temperature and normal pressure on the inlet side of the supercharger 32 is set, and denitration bypass flow rate is operated so that the inlet temperature of the supercharger 32 may be the normal temperature and supercharger 32 bypass flow rate is operated so that the inlet pressure of the supercharger 32 may be the normal pressure.