In a motor drive control system configured to include a converter capable of stepping up the voltage, when the locked state of MG2 operating as an electric motor does not occur (NO in S130), a voltage command value VHref for the converter output voltage is set according to respective required voltages of MG1 operating as an electric generator and MG2 (S140). In contrast, when the locked state of MG2 occurs (YES in S130), the voltage command value VHref is set to a limit voltage Vlmt or less for limiting the voltage step-up by the converter (S150, S180). When the locked state occurs, the converter output voltage is decreased and accordingly the DC voltage switched by the inverter is lowered, so that a switching loss at the switching device forming a part of the inverter is reduced and the temperature increase due to the heat generation can be suppressed.