A plurality of current sensors are provided to correspond to a plurality of inverter circuits for driving a plurality of motor generators, respectively. Zero point adjustment of each current sensor is executed in a non-energized state recognized based on a stop of operation of the corresponding inverter circuit and when noise influence is determined to be small based on stops of operations of the other inverter circuits in the same casing. As a result, it is possible to avoid a risk of performing the zero point adjustment in a state in which an output of the current sensor is not exactly a value corresponding to zero current due to the noise influence from the other inverter circuits. In this way, it is possible to highly accurately execute the zero point adjustment of the current sensor for measuring motor driving current.