A gas fuel injection valve is provided in which a circular recess is formed in a front end face of a valve plunger, the circular recess being surrounded by an annular land part, which is an outer peripheral part of the front end face, an inner peripheral face of the circular recess is formed in a tapered shape so as to increase in diameter in going from a base of the circular recess toward the annular land part, an annular lip is formed on a seating member, the annular lip being joined from the inner peripheral face through to the annular land part and being seated on a valve seat, and the annular lip is disposed so that an annular ridge line of an apex of the annular lip is positioned, in a projection in the axial direction of the valve plunger, above the inner peripheral face.