A gas fuel injection valve is provided in which a single nozzle member (11) is fixedly provided in a front end part of a valve housing (2), and this nozzle member (11) has formed therein a valve seat (13), a valve hole (45) extending through a central part of the valve seat (13), a throttle hole (46) having a smaller diameter than that of the valve hole (45) and communicating with an outlet of the valve hole (45), and a nozzle hole (48) having a larger diameter than that of the throttle hole (46) and communicating with an outlet of the throttle hole (46), wherein when an internal diameter of the throttle hole (46) is D1, a length of the hole (46) is L1, an internal diameter of the nozzle hole (48) is D2, and a length of the nozzle hole (48) is L2, L1/D1>1  (1) 1