The present invention relates to a planographic printing plate employed in the field of offset printing, and more particularly, to a preparation method for a printing plate employing a conventional planographic printing original plate with a novel light source. In this method, an image is formed to a planographic printing original plate, in which at least one photosensitive layer sensitive in the region of 300 nm˜450 nm is provided on a substrate, by scan irradiating the plate with high density energy light in the form of the image, and then performing wet development and a post-treatment. This preparation method for the printing plate is characterized in that the output wavelength of the high density energy light is within the range of 300 nm or more, but less than 370 nm, and the high density energy light is high density energy light of the second or third harmonic obtained from a solid-state semiconductor or a solid-state exited by semiconductor. By means of this method, it is possible for an image to be directly drawn stably and at low cost to a conventional planographic printing original plate that was manufactured for an application with active rays, by employing high density energy light that is scan irradiated according to digital information. As a result, high resolution images can be reproduced easily.