PURPOSE: To prevent the generation of distortion, by providing zigzag faces having the same shape, one of which becomes a roof mirror surface at least, on front and rear faces so that mountains and valleys of one zigzag face oppose to valleys and mountains of the other and providing the holding frame so as to surround the center part along both zigzag faces.

CONSTITUTION: In a plastic roof mirror array formed by injection molding, a zigzag face 1 which becomes a roof mirror surface and a zigzag face 2 which does not become a roof mirror surface are provided through a holding frame 3, which is provided so as to surround the center part of these faces, so that mountains and valleys of one zigzag face oppose to valleys and mountains of the other. Since the holding frame 3 is brought to the center between zigzag faces 1 and 2, the contraction stress in molding becomes uniform, and the generation of distortion such as warp is prevented.