A control device for a multiple motor comprises: a drive unit constituted by a pair of upper and lower arm switching elements for driving the multiphase motor; a single current detection circuit for detecting a current value; a PWM signal generation unit for generating a plurality of first phase PWM signals within two control cycles on the basis of the current value and a carrier signal; a phase shift control unit for shifting a first PWM signal with a prescribed phase generated by the PWM signal generation unit by gradually changing the amount of phase shift within the two control cycles, and outputting the shifted first PWM signal to the drive unit; and a current detection observer for estimating a current value for the multiphase motor on the basis of the current value. The PWM signal generation unit generates a plurality of second phase PWM signals within two control cycles on the basis of the estimated current value and carrier signal. When the phase shift amount in a prescribed phase in the control cycle immediately before the present control cycle is zero and the phase shift amount in a prescribed phase in the present control cycle is not zero, the phase shift control unit gradually increases the shift amount from zero in the present control cycle and the next control cycle to thereby use the second phase PWM signals in the next control cycle.