To provide a fuel injection nozzle 20 capable of stably injecting fuel, and preventing the nozzle body 23 from being deformed since it is cooled by cooling air and maintained at a predetermined position without being affected by an external force applied to the fuel injection nozzle 20.

The fuel injection nozzle 20 is attached to a cylinder head 3. A cylindrical retaining nut 25 is fitted to a nozzle holder 21 and a nozzle body 23. The fuel injection nozzle is disposed in such a manner that the retaining nut 25 vertically extends through a cooling air passage 3c horizontally formed in the cylinder head 3.