A integrally formed synthetic resin lower sash for an automotive vehicle door structured so as to be disposed within a door panel and guide a window glass received within the door panel in a vertical direction. In order to reduce a frictional sound generated between a moving glass and the lower sash, the lower sash is constituted by an outer wing, an inner wing and a frame surrounding an edge portion of the window glass, a plurality of extending portions projecting toward the surface of the opposing window glasses and intermittently disposed to a direction of guiding the window glass are provided in the outer wing and the inner wing, and a projecting piece slidably in contact with each of inner and outer surfaces of the glass is extended in such a manner as to continue from the expanding portion, thereby forming a glass guide.