A torque command (Tht) used in the calculation of a voltage command (Vht) of a voltage-up converter is generated by adding an upper limit value value (Tc_max) of damping control that can be set by a motor drive device with a target drive torque (Tbt). Accordingly, the torque command (Tht) exhibits a waveform absent of variation, differing from a torque command (Tcmd) that is generated by adding damping torque generated based on revolution count variation component with the target drive torque (Tbt). Therefore, the voltage command (Vht) calculated based on the torque command (Tht) exhibits a waveform absent of variation. Accordingly, increase in current passing through the voltage-up converter caused by variation in the voltage command (Vht) can be suppressed. As a result, power loss at the voltage-up converter is reduced and operation of the motor at high efficiency can be realized. Further, the voltage-up converter can be protected from element fracture.