A magnet temperature estimating device for a motor including a rotor having magnets and configured to output a rotational motive force, and a stator having a plurality of coils opposing the rotor with a gap therebetween, is provided. The device includes a sensor configured to detect an induced voltage induced by rotation of the rotor, and a controller configured to control the motor by supplying power to the plurality of coils in response to an input of a detection signal from the sensor. Gaps adjacent to each magnet in a rotation direction of the rotor are formed in the rotor. The controller estimates a temperature of the magnet based on the induced voltage detected when the magnet opposes any one of the plurality of coils, according to the rotation of the rotor.