Abstract: A wave reducer includes a cam, a flex gear, an internal gear, an angle sensor, a thrust sensor, and a circuit. The angle sensor is located in the flex gear and an output value thereof changes in accordance with a rotation angle of the cam. The thrust sensor is located in the flex gear and an output value thereof changes according to a thrust force applied to the cam. The circuit is electrically connected with the angle sensor and the thrust sensor. The circuit corrects an output value of the angle sensor based on an output value of the thrust sensor.