An erecting equal-magnification lens array plate includes a stack of a plurality lens array plates built such that pairs of corresponding lenses form a coaxial lens system, where each lens array plate is formed with a plurality of convex lenses on both surfaces of the plate. The plate receives light from a substantially straight light source facing one side of the plate, and the plate forms an erect equal-magnification image of the substantially straight light source on an image plane facing the other side of the plate. A light shielding member operative to shield light not contributing to imaging is formed in the neighborhood of a position in the intermediate plane in the erecting equal-magnification lens array plate where an inverted image of the substantially straight light source is formed. The main lens arrangement direction of the convex lenses differs from the main scanning direction of the erecting equal-magnification lens array plate.