A current command value computation section 22 is provided with a q-axis current command value correction section 31 and an expected voltage utilization factor computation section 32. The expected voltage utilization factor computation section 32 estimates an expected voltage utilization factor f based on a rotational angular velocity ω of a motor 12, a q-axis current command value Iq*, and a power voltage Vb (the maximum voltage Vmax). The expected voltage utilization factor f is the ratio of required output voltage to the maximum voltage Vmax applicable to a drive circuit 18. Based on the expected voltage utilization factor f, the q-axis current command value correction section 31 corrects the q-axis current command value Iq* such that the corrected expected voltage utilization factor f does not exceed a predetermined value that corresponds to the voltage saturation limit.