The sensor arrangement structure includes a pulley that rotates about a rotation axis; and a sensor that detects rotation of the pulley. The pulley includes a fixed pulley, a movable pulley that can be displaced relative to the fixed pulley in a direction of the rotation axis, and a plunger defining an oil chamber on a back of the movable pulley. The plunger is provided with a detection target portion in a region that can be visually recognized from the direction of the rotation axis, and the sensor is provided on a support portion that rotatably supports the fixed pulley in a direction along the rotation axis and faces the region in which the detection target portion is provided.