PURPOSE: To reduce the slanting of a sleeve and increase the strength of a fuel injection nozzle by providing a piston member having a stepped external surface and slidable in a stepped cylinder, and defining an annular chamber connected to a fuel inlet by the stepped portion of the cylinder.

CONSTITUTION: A spacer 12 defines a bore 24 with a piston member of the shape of a sleeve 25 slidable arranged therein. The sleeve 25 has a thin end portion in the vicinity of a nozzle body 10, and is step-shaped. The bore 24 is also stepped, with the stepped portion thereof defining an annular chamber 26 around the sleeve. Thud a stepped portion if formed on the external surface of the sleeve 25, therefore the force acting on the sleeve due to the fuel pressure of a fuel inlet can be adjusted easily.