To improve exhaust characteristics by promoting mixture of intake with EGR gas while utilizing intake to be introduced into an intake manifold.

An air duct 14 is connected obliquely to an intake manifold 12 to which an introduction port 12a of EGR gas is opened, so as to cross a main flow A of intake, at its fastest velocity portion, with outflow direction B of the EGR gas, in the vicinity of an inner wall of the intake manifold 12. Mixture of the intake with the EGR gas is thus promoted by the main flow A of the intake having the fastest velocity. It is thus possible to equalize the EGR gas amounts introduced to respective cylinders, and evenly reduce NOx discharge amounts independently on the cylinders, accompanied with lowering of combustion temperature.