An internal combustion engine is provided in which an exhaust port communicating with a combustion chamber formed in a cylinder head is formed from independent exhaust ports, which are positioned on the upstream side, and a grouped exhaust port, in which the plurality of independent exhaust ports are combined. Water supplied from a supply pump passes through a water passage of the grouped exhaust port and a water passage of the independent exhaust ports while cooling the exhaust port, and a valve seat and valve guide on the periphery of the exhaust port, which have high temperatures, thus heating the water itself and thereby recovering waste heat of the internal combustion engine. The heated water carries out heat exchange with exhaust gas in an evaporator provided in an exhaust passage and turns into high temperature, high pressure steam, which drives an expander of a Rankine cycle system. It is thereby possible to maximize the recovery of heat transferred from the exhaust port to the cylinder head of the internal combustion engine.