To ensure flexibility in design by eliminating the need of arranging a power unit and a vehicle body frame on both inner/outer sides of a swing arm, and to sufficiently ensure the stiffness of a shaft member, in a swing arm supporting means wherein a pair of right and left supporting arm portions extending forward is provided at a front part of the swing arm journaling a rear wheel at a rear part, and wherein both supporting arm portions are rockably supported by a swing arm supporting means disposed between the supporting arm portions through a shaft member.

An outer end portion of the shaft member 72 penetrating at least one supporting arm portion 71c of both supporting arm portions 70b, 70c is held by a shaft holding member 97 detachably attached to a swing arm supporting means PA.