The present invention prevents a coil of a phase other than a coil of a specific phase from being adversely affected by heat even when motor torque varies or the state of current distribution to a three-phase coil varies. The present invention comprises: a motor torque obtaining unit that obtains motor torque output by a three-phase alternating current motor; a current distribution state obtaining unit that obtains the state of current distribution to coils of respective phases of a stator of the three-phase alternating current motor; a temperature sensor that detects the temperature of a coil of a specific phase out of the three-phase coil as a coil sensor temperature; and a motor torque control unit that controls the motor torque by updating an other phase estimated temperature, which is an estimated temperature of a coil of another phase that is a coil other than the coil of the specific phase out of the three phase coil, using an integrated value of a temperature increase per unit time at each time point of the coil of the other phase, and by using at least the other phase estimated temperature. The temperature increase per unit time of the coil of the other phase at each time point is determined by the motor torque control unit in accordance with a combination of the motor torque and the current distribution state at the time point.