A controller of a multi-phase electric motor includes a drive section for driving the multi-phase electric motor, a single current detection section for detecting a current value of the multi-phase electric motor, a pulse width modulation signal (PWM) generation section for generating a PWM signal of each phase based on the current value detected by the current detection section and a saw-tooth signal having a predetermined frequency, a current detectability determination section for determining whether or not the current value is detectable in the current detection section based on the PWM signal of each phase generated by the PWM signal generation section, and a switching number determination section for determining whether or not conducting number of the upper arm switching element is an even number or an odd number based on the determination that the current is not detectable by the current detectability determination section.