An anomaly determining device includes a sensor information acquirer and a determiner. The sensor information acquirer acquires sensor information output in time sequence from each of two sensors that detect different physical quantities of a moving part that is subjected to positioning control. The determiner determines, when the moving part is located within a predetermined range from a target position for positioning, the presence or absence of an anomaly in at least one of the two sensors in accordance with the acquired sensor information and outputting a result of the determination.