A plate making method for making a printing plate from a printing plate material, this plate making method including an image output process for outputting an image onto the printing plate material in conformity to the first control strip image data which form a pseudo gradation in the two-dimensional direction having the density gradation in the longitudinal direction and the second control strip image data which form a pseudo gradation being different from the abovementioned pseudo gradation in the two-dimensional direction and having a uniform density in the longitudinal direction, and an image forming process for forming on this printing plate an image 1 based on the first control strip image data, and an image 2 based on the second control strip image data.
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