The charge-discharge power demand is set to the charging power, when the state of charge of the battery is less than the reference value or when the state of charge of the battery is more than or equal to the reference value and less than the reference value while the vehicle power demand is less than reference value. The charge-discharge power demand is set to the discharging power, when the state of charge of the battery is more than or equal to the reference value or when the state of charge of the battery is more than or equal to the reference value and less than the reference value and while the vehicle power demand is more than or equal to the reference value. The charge-discharge power demand is set without change in value to the last set the charge-discharge power demand, when the state of charge of the battery is more than or equal to the reference value and less than the reference value while the vehicle power demand is more than or equal to the reference value and less than the reference value. The engine and the motors are so controlled as the battery is charged or discharged with the charge-discharge power demand and the vehicle is driven with vehicle power demand.