A driving force connecting/disconnecting device includes an externally toothed spline provided on an outer periphery of one of a first shaft member and a second shaft member, an internally toothed spline engageable with the externally toothed spline, a sleeve provided with the internally toothed spline which is engageable with the externally toothed spline by moving in an axis line direction and connecting the first shaft member and the second shaft member for transmitting the driving force, a moving mechanism which moves the sleeve in the axis line direction, a holder which holds the sleeve and the moving mechanism, and a positioning mechanism for positioning the holder in the axis line direction by bringing the holder into contact with the one of the first shaft member and the second shaft member thereby to mount the holder to the first shaft member.