To improve sensitivity, image strength, developing property, gradient property, inking property, printing durability, and halftone dot reproducibility by a method wherein the reflectance of the surface of an aluminum supporting body before a layer of a photo-sensitive composition is provided, is kept within a range of a specified percentage.

For an aluminum supporting body, it is preferable to apply a degreasing treatment in order to remove a rolling oil on the aluminum surface prior to a surface- roughening. As a surface-roughening method, there are a so-called mechanical roughening method wherein the surface is mechanically roughened, and a so-called electro-chemical roughening method wherein the surface is electro-chemically roughened. Then, an anodizing is applied to the surface-roughened aluminum plate, and the aluminum supporting body is obtained. the aluminum supporting body is obtained by performing the surface-roughening treatment and the anodizatin in such manners, and that the reflectance (which is normally an absorption wavelength of the layer of a photo-sensitive composition being applied on the top, and especially is a reflectance when ultraviolet rays of 350-400 nm are used) of the surface of the aluminum supporting body is 50-70%, is an essential requirement.