This motor device includes: a motor having components including a stator and a rotor; and a controlling circuitry to control the motor. The motor is provided with temperature sensors to detect a heat transfer amount and a transfer direction about the components. The controlling circuitry includes a temperature calculator to calculate a component temperature based on a thermal circuit network from thermal resistances and heat capacities given for the components. On the basis of actual measured values of the heat transfer amount and the transfer direction obtained by the temperature sensors, the temperature calculator corrects thermal resistances and heat capacities about the components obtained on the basis of the thermal circuit network, and estimates the temperature of each component during driving of the motor.