SWING ARM

A swing arm having a reduced number of parts in which manufacturing cost can be reduced. In a swing arm including: vehicle-body-side support portions that are supported on a vehicle body side by a first rotary shaft; wheel-side support portions that are supported on a wheel side by a second rotary shaft; and a pair of arm portions that connect the vehicle-body-side support portions and the wheel-side support portions to each other, cross members that extend in an axial direction of the first rotary shaft is arranged on the pair of arm portions so as to extend between the pair of arm portions, and the cross members have a U shape in cross section orthogonal to a longitudinal direction of the cross members, thus forming opening portions that open so as to face a direction that the pair of arm portions extends.