Abstract: A tip end surface of a valve body and a back end surface of an injection nozzle contact each other with pressure by being fastened using a retaining nut and thereby form a metal seal structure to achieve a metal seal. To increase a surface pressure in a seal surface by fastening axial force, conventional recesses around the central axis of a nozzle are replaced so that proximity of a high pressure fuel hole is secured as a seal surface. An outside recess is provided outside of the proximity of the high pressure fuel hole to link with an outer peripheral border of the metal seal structure. Alternatively, a contact surface functioning as a retaining seal surface is added outside of the outside recess to be apart from the proximity of the high pressure fuel hole.