A control device performs voltage conversion control on a voltage conversion circuit between a power supply and motor control circuits which control a plurality of motors. The control device includes sampling units for sampling a DC voltage after voltage conversion, target voltage setting units for setting target voltages VHT1 and VHT2 of the plurality of motors, selection unit for selecting a target voltage VHT to be converted by the voltage conversion circuit from a plurality of target voltages VHT1 and VHT2, generating unit for generating a sampling timing TS on the basis of a gate signal GS1 or GS2 of one of the motors with the target voltage which has not been selected, and control unit for performing the voltage conversion control using the DC voltage sampled by the sampling units at the sampling timing TS in response to each sampling timing request DS in the voltage conversion control.