A structure for supporting a swing arm in a motorcycle is provided in which a power unit swingably supports a front portion of the swing arm via a first pivot of a cylindrical shape that is coaxial with an output shaft of the power unit and a second pivot that is coaxial with the first pivot. The number of parts used are reduced and the removal and installation of the swing arm is facilitated. An output shaft, an outer end portion of which projects outwardly of a swing arm, is connected to a final transmission member of a reduction transmission and is capable of removal or insertion in an axial direction, while being incapable of relative rotation about an axis. A first pivot is removably mounted on a power unit. A second pivot is removably secured to the power unit PA or the swing arm.