A vehicle drive system, comprising: a motor configured to generate driving force for drive wheels; an inverter (15a, 15b) electrically connected to the motor; a battery unit configured to supply electric power to the inverter (15a, 15b); and a control unit configured to control operation of the inverter (15a, 15b), wherein the battery unit has serially-connected first and second batteries (18a, Battl, 18b, Batt2), and a negative pole of the first battery (18a, Batt1) and a positive pole of the second battery (18b, Batt2) are mutually connected, and the control unit is configured to control the operation of the inverter (15a, 15b) so that a voltage output from the inverter (15a, 15b) to the motor is higher than an output voltage of the first battery (18a, Batt1) and also than an output voltage of the second battery (18b, Batt2), characterized in that the negative pole of the first battery (18a, Batt1) and the positive pole of the second battery (18b, Batt2) that are mutually connected are grounded, the vehicle drive system further comprises a balance circuit configured to balance charged amounts of the first and second batteries (18a, Battl, 18b, Batt2) by performing charge/discharge control between the first and second batteries (18a, Battl, 18b, Batt2), the balance circuit including first and second switches (S4, S5) serially connected between a positive pole and the negative pole of the first battery (18a, Batt1), third and fourth switches (S6, S7) serially connected between the positive pole and a negative pole of the second battery (18b, Batt2), and a capacitor of which one end is connected to a node of the first switch and the second switch and the other end is connected to a node of the third switch and the fourth switch, and the vehicle drive system further comprises a controller configured to control on/off of the first to fourth switches (S4, S5, S6, S7) of the balance circuit, and to determine which of the first and second batteries (18a, Battl, 18b, Batt2) has greater energy, and if the first battery (18a, Batt1) has greater energy than the second battery (18b, Batt2), to perform a first operation of turning on the first and third switches and turning off the second and fourth switches, and thereafter to perform a second operation of turning off the first and third switches and turning on the second and fourth switches, and and if the second battery (18b, Batt2) has greater energy than the first battery (18a, Batt1), to perform the second operation and thereafter to perform the first operation. a motor configured to generate driving force for drive wheels; an inverter (15a, 15b) electrically connected to the motor; a battery unit configured to supply electric power to the inverter (15a, 15b); and a control unit configured to control operation of the inverter (15a, 15b), wherein the battery unit has serially-connected first and second batteries (18a, Battl, 18b, Batt2), and a negative pole of the first battery (18a, Batt1) and a positive pole of the second battery (18b, Batt2) are mutually connected, and the control unit is configured to control the operation of the inverter (15a, 15b) so that a voltage output from the inverter (15a, 15b) to the motor is higher than an output voltage of the first battery (18a, Batt1) and also than an output voltage of the second battery (18b, Batt2), characterized in that the negative pole of the first battery (18a, Batt1) and the positive pole of the second battery (18b, Batt2) that are mutually connected are grounded, the vehicle drive system further comprises a balance circuit configured to balance charged amounts of the first and second batteries (18a, Battl, 18b, Batt2) by performing charge/discharge control between the first and second batteries (18a, Battl, 18b, Batt2), the balance circuit including first and second switches (S4, S5) serially connected between a positive pole and the negative pole of the first battery (18a, Batt1), third and fourth switches (S6, S7) serially connected between the positive pole and a negative pole of the second battery (18b, Batt2), and a capacitor of which one end is connected to a node of the first switch and the second switch and the other end is connected to a node of the third switch and the fourth switch, and first and second switches (S4, S5) serially connected between a positive pole and the negative pole of the first battery (18a, Batt1), third and fourth switches (S6, S7) serially connected between the positive pole and a negative pole of the second battery (18b, Batt2), and a capacitor of which one end is connected to a node of the first switch and the second switch and the other end is connected to a node of the third switch and the fourth switch, and the vehicle drive system further comprises a controller configured to control on/off of the first to fourth switches (S4, S5, S6, S7) of the balance circuit, and to determine which of the first and second batteries (18a, Battl, 18b, Batt2) has greater energy, and if the first battery (18a, Batt1) has greater energy than the second battery (18b, Batt2), to perform a first operation of turning on the first and third switches and turning off the second and fourth switches, and thereafter to perform a second operation of turning off the first and third switches and turning on the second and fourth switches, and and if the second battery (18b, Batt2) has greater energy than the first battery (18a, Batt1), to perform the second operation and thereafter to perform the first operation.