One of coaxially placed two output shafts which is located on the inner outer side is a first shaft 102, and the other one which is located on the outer side is a second shaft 104. The first shaft 102 projects more than the second shaft 104. A first clutch disk 116 is connected to a projecting portion of the first shaft 102, and a second clutch disk 110 is connected to the second shaft 104 through a sleeve 106. The second shaft 104 and the sleeve 106 are splined to each other, and the sleeve 106 and the second clutch disk 110 are splined to each other. According to this, the sleeve 106 is structurally permitted to move in an axial direction of the engaging/disengaging mechanism, and the first clutch disk 116 is engaged and disengaged by the movement of the sleeve 106 in the axial direction.