A motorcycle wherein only air can be communicated between the inside and the outside of a gear case without increasing the size of the gear case. A gear case includes a gear case body and a gear case cover. The gear case body includes a breather chamber of a labyrinth structure which continues in a circumferential direction of a rear wheel and extends in an upward and downward direction. An upper end of the breather chamber is in communication with a breather path and is open to atmospheric air while a lower end of the breather chamber is in communication with a gear chamber through a slit extending in a widthwise direction of the rear wheel.