The object of the invention is to provide an optical reflection plate having the following merits A - D. A. There is no need for expensive initial cost for a mold and the like for making a three-dimensional shape. B. Processing is simple and processing cost is low. C. The reflection plate shape after bending can be accurately retained and moreover the reflection plate is superior in dimensional stability even under endurance conditions. D. The attachment processing method for shape retention is simple, and the cost is low. To achieve the above object, the invention intermittently forms narrow cuts, along straight lines, that pass through from one-side surface to the other-side surface in a light-reflecting foamed plastic film or sheet. Thereafter, the film or sheet is bent along the cuts.