A gas passage that is connected to an exhaust passage and a water passage that is connected to a water jacket are formed in a turbine housing. The water passage and the gas passage are arranged adjacent to each other in an exhaust gas-introducing side joint part of the turbine housing, and a mating face in which the water passage opens and a mating face in which the gas passage opens are formed not to connect smoothly to each other. The turbine housing is attached to the cylinder head with an O-ring that prevents leakage of coolant interposed between the mating face and the cylinder head, and a seal member that prevents leakage of exhaust gas interposed between the mating face and the cylinder head.