A hollow panel includes a panel body and a guide rail member joined thereto. The panel body is formed in a structure such that two plate-like members are joined by many ribs. The panel body includes an open space portion and a closed space portion. The open space portion is formed so as to extend in the extrusion direction of the panel body and is formed as an open space in a cross-section perpendicular to the extrusion direction. The closed space portion has a shape such that a plurality of closed spaces are defined by the ribs between the plate-like members in a cross-section perpendicular to the extrusion direction. The guide rail member is press-fitted into the open space portion.