A vehicle electric drive system and a hybrid engine-motor type vehicle drive system realizing simplification and miniaturization of electric parts and, moreover, reduction in cost while maintaining performances can be provided. A part 1 of wheels is driven by an engine. The wheels are driven by a motor as necessary. The motor, a generator, and an accessory battery are connected to each other via a voltage step-up/step-down device. The voltage step-up/step-down device has a function of stepping up power of the battery and supplying the stepping up power to the motor, and a function of stepped down power of the generator and supplying the stepped down power to the battery and the accessories.