An air ventilation device of a vehicle includes: a housing including an air inlet and an air outlet and a cooling core and a heating core disposed between the air inlet and the air outlet; a rear extending flow path extending to the rear of the vehicle, and having a first end connected to the air outlet of the housing and a second end connected to a back seat air vent disposed to face a back seat space; an air collecting flow path directly connecting the rear extending flow path and the air inlet of the housing; and an opening and closing door structure opening and closing air circulation between the rear extending flow path and the air outlet and air circulation between the air collecting flow path and the air inlet.