The invention provides a roof reinforcement member including an extruded aluminum alloy part which is upwardly convex and extends in a vehicle lateral direction. The extruded aluminum alloy part includes a pair of upper and lower flanges approximately parallel-facing each other as seen in a cross-section thereof and a pair of webs formed to stand along the vehicle height direction. The pair of flanges and the pair of webs form a closed sectional part. The pair of flanges each have a projecting flange portion. In the cross-section, the lower flange is thicker than the upper flange and/or the lower flange is wider than the upper flange, and the neutral axis of upward/downward bending is positioned lower than the middle of the height of the cross-section. This arrangement can reduce the stress generated on the lower side of the cross-section when the extruded aluminum alloy part is bent, so that the extruded aluminum alloy part can be effectively made stronger against deformation.