A sensor mounting structure includes a positioning member, a holding member, and a biasing member. The positioning member is a mounting reference of a sensor. The holding member is attachable to and detachable from the positioning member so as to form a space in which the sensor is disposed with respect to the positioning member. The biasing member includes an arched part which is overhung between a pair of engaging parts engaging with the holding member. The biasing member, while the holding member is attached to the positioning member, elastically deforms the arched part that is sandwiched between the holding member and the sensor that is disposed in the space so as to bias the sensor to the positioning member.