A four-wheel drive hybrid vehicle, comprising: a first pair of drive wheels disposed on a front side or rear side of a vehicle body; a second pair of drive wheels disposed on the other side of the vehicle body; an engine that is disposed on a side of the first pair of drive wheels; a first motor that is arranged to generate a torque to be added to an output torque of the engine; an exhaust pipe for discharging exhaust gas of the engine from a rear side of a vehicle body; a first propeller shaft that is arranged to deliver an output power of the engine to the second pair of drive wheels; a transfer that is arranged to distribute the output power of the engine to the first pair of drive wheels; a second propeller shaft arranged on the other side of the first propeller shaft from the exhaust pipe in a width direction of the vehicle body, the second propeller shaft arranged to deliver a drive force from the transfer to the first pair of drive wheels; a second motor having a generating function, which is arranged to apply torque to the first pair of drive wheels, and to which torque of the first pair of drive wheels is applied, in use; and a transmission device comprising: a planetary gear unit, the planetary gear unit comprising a sun gear, a ring gear as an internal gear arranged concentrically with the sun gear, a plurality of pinion gears interposed between the sun gear and the ring gear, and a carrier supporting the pinion gears in a rotatable manner, wherein the carrier is connected to the second propeller shaft; and an engagement device; wherein: the transmission device is arranged to selectively connect the second motor to the second propeller shaft in a torque transmittable manner; and the engagement device is disposed between the ring gear and a stationary member and is arranged to be engaged such that the planetary gear unit serves as a speed reducing device that transmits torque of the second motor to the second propeller shaft, and arranged to be disengaged to bring the speed reducing device into a neutral state in which the torque is not transmitted through the planetary gear. a first pair of drive wheels disposed on a front side or rear side of a vehicle body; a second pair of drive wheels disposed on the other side of the vehicle body; an engine that is disposed on a side of the first pair of drive wheels; a first motor that is arranged to generate a torque to be added to an output torque of the engine; an exhaust pipe for discharging exhaust gas of the engine from a rear side of a vehicle body; a first propeller shaft that is arranged to deliver an output power of the engine to the second pair of drive wheels; a transfer that is arranged to distribute the output power of the engine to the first pair of drive wheels; a second propeller shaft arranged on the other side of the first propeller shaft from the exhaust pipe in a width direction of the vehicle body, the second propeller shaft arranged to deliver a drive force from the transfer to the first pair of drive wheels; a second motor having a generating function, which is arranged to apply torque to the first pair of drive wheels, and to which torque of the first pair of drive wheels is applied, in use; and a transmission device comprising: a planetary gear unit, the planetary gear unit comprising a sun gear, a ring gear as an internal gear arranged concentrically with the sun gear, a plurality of pinion gears interposed between the sun gear and the ring gear, and a carrier supporting the pinion gears in a rotatable manner, wherein the carrier is connected to the second propeller shaft; and an engagement device; wherein: a planetary gear unit, the planetary gear unit comprising a sun gear, a ring gear as an internal gear arranged concentrically with the sun gear, a plurality of pinion gears interposed between the sun gear and the ring gear, and a carrier supporting the pinion gears in a rotatable manner, wherein the carrier is connected to the second propeller shaft; and an engagement device; wherein: the transmission device is arranged to selectively connect the second motor to the second propeller shaft in a torque transmittable manner; and the engagement device is disposed between the ring gear and a stationary member and is arranged to be engaged such that the planetary gear unit serves as a speed reducing device that transmits torque of the second motor to the second propeller shaft, and arranged to be disengaged to bring the speed reducing device into a neutral state in which the torque is not transmitted through the planetary gear.