PROBLEM TO BE SOLVED: An object of the present invention is to sufficiently spread the spray generated by injection of fuel from a nozzle hole, ensures further minute fuel microparticles in spraying, and ensures the further homogeneous fuel microparticles in spraying. SOLUTION: The fuel flowed from the guide channels 18, 20 into the swirl chamber 13 is guided to the nozzle hole 6 while swirling in the swirl chamber 13 in the identical direction. The nozzle hole 6 is divided into a portion near a fuel-inflow end 51 and a portion near a fuel-outflow end 52. The portion near the fuel-outflow end 52 of the nozzle holes 6 is formed so as to have a flow passage cross-sectional area gradually increasing towards a fuel outflow-side opening end 6b, and includes a curved surface 54 formed by smoothly connecting an inner surface of the nozzle holes 6 at upstream end side in a fuel flow direction to an inner surface of the nozzle holes 6 at the portion near the fuel-inflow end 51 so as to smoothly and gradually increase the flow passage cross-sectional area. The curved surface 54 is configured to ensure further thin film-like flow by expanding a flow of the fuel in the nozzle holes 6 by means of Coanda effect.