A wheel speed sensor mounting structure comprising: a wheel support member supported by a vehicle body and configured to support a wheel; and a wheel speed sensor detecting a rotation speed of the wheel, wherein the wheel speed sensor is disposed on an inner side of the wheel support member in a vehicle width direction and is disposed in a region surrounded by an axle of the wheel and chassis component attachment parts (38c1 and 38c2) of the wheel support member in a side view, wherein the wheel speed sensor mounting structure further comprising: a first positioning part provided on the inner side of the wheel support member in the vehicle width direction, adjacent to a sensor fastening part which fastens the wheel speed sensor, and used for positioning of the wheel speed sensor; and a second positioning part provided on the inner side of the wheel support member in the vehicle width direction, separated from the sensor fastening part and the first positioning part, and used for positioning of the wheel speed sensor in a rotational direction with respect to a center of the fastening part, wherein the wheel speed sensor is covered with a protective member and fastened to the wheel support member together with the protective member, characterized in that the second positioning part includes a surrounding part formed to follow an engaged part at a portion engaging with the engaged part of the wheel speed sensor, and wherein the wheel speed sensor is mounted on the wheel support member in a state in which it is sandwiched between a holding part provided in the protective member and the first positioning part provided on the inner side of the wheel support member in the vehicle width direction. a wheel support member supported by a vehicle body and configured to support a wheel; and a wheel speed sensor detecting a rotation speed of the wheel, wherein the wheel speed sensor is disposed on an inner side of the wheel support member in a vehicle width direction and is disposed in a region surrounded by an axle of the wheel and chassis component attachment parts (38c1 and 38c2) of the wheel support member in a side view, wherein the wheel speed sensor mounting structure further comprising: a first positioning part provided on the inner side of the wheel support member in the vehicle width direction, adjacent to a sensor fastening part which fastens the wheel speed sensor, and used for positioning of the wheel speed sensor; and a second positioning part provided on the inner side of the wheel support member in the vehicle width direction, separated from the sensor fastening part and the first positioning part, and used for positioning of the wheel speed sensor in a rotational direction with respect to a center of the fastening part, wherein the wheel speed sensor is covered with a protective member and fastened to the wheel support member together with the protective member, characterized in that the second positioning part includes a surrounding part formed to follow an engaged part at a portion engaging with the engaged part of the wheel speed sensor, and wherein the wheel speed sensor is mounted on the wheel support member in a state in which it is sandwiched between a holding part provided in the protective member and the first positioning part provided on the inner side of the wheel support member in the vehicle width direction. a first positioning part provided on the inner side of the wheel support member in the vehicle width direction, adjacent to a sensor fastening part which fastens the wheel speed sensor, and used for positioning of the wheel speed sensor; and a second positioning part provided on the inner side of the wheel support member in the vehicle width direction, separated from the sensor fastening part and the first positioning part, and used for positioning of the wheel speed sensor in a rotational direction with respect to a center of the fastening part, wherein the wheel speed sensor is covered with a protective member and fastened to the wheel support member together with the protective member, characterized in that the second positioning part includes a surrounding part formed to follow an engaged part at a portion engaging with the engaged part of the wheel speed sensor, and wherein the wheel speed sensor is mounted on the wheel support member in a state in which it is sandwiched between a holding part provided in the protective member and the first positioning part provided on the inner side of the wheel support member in the vehicle width direction.