A covering body (10) made of a synthetic resin and including a rear shoulder part (16) oriented toward a fuel inlet part (6) side is formed around an outer periphery of an intermediate portion in an axial direction of a fuel injection valve (I). The rear shoulder part (16) includes: a first semicircular shoulder part (16a) extending over a half periphery of the covering body (10); a second semicircular shoulder part (16b) shifted in the axial direction with respect to the first semicircular shoulder part (16a) and extending over the other half periphery of the covering body (10); and a standing wall (16c) standing to connect the first and second semicircular shoulder parts (16a, 16b). On a front end of a fuel supply cap (20), a semicircular holding surface (28b) holding at least one of the first and second semicircular shoulder parts (16a, 16b) to prevent the fuel injection valve (I) from being fallen off from the mounting hole (2), and a rotation stopper surface (28c) abutting against the standing wall (16c) to prevent rotation of the fuel injection valve (I) are formed. Accordingly, it is possible to provide a fuel injection valve mounting structure including positioning means capable of firmly restricting an orientation of a coupler in a given direction without forming projections on a fuel injection valve and a fuel supply cap.