A motor controller includes: an estimated temperature calculating section that calculates and stores an estimated temperature of a motor, and a control section that can perform a drive control of the motor only when this estimated temperature is not larger than a predetermined value. When the motor is stopped, a second temperature gradient while the temperature of the motor decreases from a stop-time temperature to a predetermined first set temperature is stored in correspondence to the stop-time temperature. The first temperature gradient corresponding to the estimated temperature at a time when the motor is stopped is calculated by using the first temperature gradient storing means, if the estimated temperature stored in the estimated temperature storing means when the motor is stopped is larger than the first set temperature. The estimated temperature stored in the estimated temperature storing means is updated according to a lapse of a stopping time of the motor by using the first temperature gradient calculated by the first temperature gradient calculating means.