A planar microlens array includes an array of convex microlenses made of an ultraviolet-curable synthetic resin having a high refractive index and disposed on a surface of a base glass plate. A cover glass plate is bonded to the array of convex microlenses by an adhesive layer made of an ultraviolet-curable synthetic resin having a low refractive index. A film made of an ultraviolet-curable synthetic resin is applied to a surface of the base glass plate remote from the array of convex microlenses. The film serves to prevent the planar microlens array from being warped when the ultraviolet-curable synthetic resin of the array of convex microlenses and the adhesive layer are cured.