A breather device (140) for a gear case (82) defining a gear chamber (83) therein, comprising a breather chamber (146) defined in a part of the gear case; a breathing hole (152) formed in a wall part defining an upper part of the breather chamber so as to communicate the breather chamber with outside; a communication hole (148, 150) formed in a wall part separating a lower part of the breather chamber from the gear chamber so as to communicate the breather chamber with the gear chamber; and a separating wall (154) extending partly across the breather chamber so as to define a circuitous passage between the breathing hole and the communication hole.