An auxiliary securing support for attaching an exterior wall material to a building frame having a plurality of vertical frame members through a securing member includes a main body and a protrusion. The main body has an elongated shape, includes a planar portion to which the securing member is fixable, and is fixable to at least one of the vertical frame members. The protrusion protrudes in a direction crossing the planar portion so as to come into contact with an upper side portion of the exterior wall material and that has a length such that the protrusion is not exposed on an external surface of the exterior wall material.