A reflex light reflector sheet is disclosed wherein both the front face and the rear face are provided with a plurality of juxtaposed convex lens surfaces, the rear face being covered by a mirror surface. In accordance with the inventionA. the lens surfaces of said front face are aspherical;B. the respective axes of the lens surfaces on said front and rear faces coincide, andC. the focal point of the lens which is defined by each lens surface on said front face for axially incident lights is located in or in the proximity of the associated lens surface on the rear face.A method for preparing such a reflex light reflector sheet is also disclosed. A plastic sheet is treated so as to render the sheet susceptible to surface deformation. The sheet is then passed through the nip of patterning rollers which rotate synchronously in opposite direction, the patterning rollers having surface patterns which are complementary to the lens surfaces.