PURPOSE: To provide an internal combustion engine which accelerates the vaporization of injected fuel in cold state, reduces production cost, and improves fuel consumption.

CONSTITUTION: As for an internal combustion engine equipped with an injector 13 which injects out fuel toward the inner wall of a suction passage 7 and a bypass passage 18 which allows the engine cooling water to make a detour around a radiator 15 in the cold engine state, a circulation water passage 9 is formed at a fuel injection position 8, and the engine cooling water in the bypass passage 18 is allowed to communicate to the circulation water passage 9. In the cold state of the engine 1, the engine cooling water which cools a cylinder head 6, etc., and is warmed to a certain degree flows in the bypass passage 18 and the circulation water passage 9 and warms the fuel injection position 8. While, the engine cooling water having a high temperature flows into the radiator 15, and prevents the increase of the temperature of the fuel injection position 8.