To stably provide a desired exhaust gas air-fuel ratio regardless of a change in the operating condition of an internal combustion engine.

This internal combustion engine 1 includes: a fuel injection valve 21 provided in an exhaust passage 12; an exhaust gas cleaning element 19 arranged downstream of the fuel injection valve; a bypass passage 40 branched upstream of the fuel injection valve 21 and merged downstream of the exhaust gas cleaning element 19; and an operating valve 24 changing the opening ratio between a main passage 12M leading from a branch to a confluent portion and the bypass passage 40. Since an exhaust gas flow rate in the main passage can be changed, even if the operating condition of the engine is changed, the desired exhaust gas flow rate in the main passage is easily provided. When regenerating the exhaust gas purifying element 19, the desired exhaust gas air-fuel ratio is stably provided.