A Laval shape is formed between the nozzle seat surface and needle tip portion. An injection hole also has the Laval shape. When the needle lift amount is small, a fuel flow velocity reaches an acoustic velocity in valve-opening portion. The fuel flow velocity further accelerated to a supersonic velocity at the Laval shape. When the needle lift amount is large, the fuel flows into the injection hole without a velocity decrease. Thus, the fuel flow velocity reaches the supersonic velocity at the Laval shape.