To provide a fuel injection device for an internal combustion engine injecting gas fuel into the internal combustion engine and capable of reducing combustion heat dissipated from a cylinder defining a combustion chamber.

The fuel injection device is used in the internal combustion engine 100, which introduces intake air to the combustion chamber 106, supplies the gas fuel into the combustion chamber 106 and has output through combustion of a mixture of the intake air and the gas fuel mixed, and comprises an injection means 2 for separately injecting a fluid B of thermal insulation and a fluid A of the gas fuel into the combustion chamber 106, wherein the injection means 2 injects the fluid B toward between a periphery of a gas fuel spray and an inner wall of the combustion chamber 106 so that it surrounds the periphery of the gas fuel spray caused by injection of the fluid A of the gas fuel.