Disclosed herein is a battery cooling duct. The duct includes a suction portion disposed between a rear seat and a floor panel of a vehicle, an inlet of the suction portion fluidly communicating with an interior of the vehicle to suction interior air. An extension portion is formed by extending an outlet side of the suction portion to a rear of the vehicle, e.g. a trunk, between the rear seat and the floor panel, and defines a passageway configured to allow the interior air to pass therethrough. A discharge portion extends from an outlet of the extension portion to the rear of the vehicle, and discharges the interior air passed through the extension portion, through an outlet of the discharge portion to the battery of the vehicle.