A heating time period is decreased by that a valve body including a hollow valve shaft is arranged in a slidable manner in a cylindrical part of a casing on which a nozzle body with a valve seat is mounted at a front end thereof, a fuel is introduced from a fuel outlet port opening on a shaft wall of the valve shaft into a fuel path formed by the valve shaft and the cylindrical part, the fuel is heated to be injected from the nozzle body by a heater arranged at an outside of the fuel path of the cylindrical part, and a sleeve is mounted in the fuel path so that a large diameter part thereof closes the fuel path at an upper area of the fuel outlet port, while a fuel inlet port is formed on a small diameter part of the sleeve to introduce the fuel into the fuel path, so that the fuel path is narrowed to decrease an amount of the fuel to be heated by the heater.