The invention relates to an image processing method and device, wherein the method contains: delivering laser light to a thermoreversible recording medium to heat the medium and record an image thereon, the medium reversibly changing a transparency or tone thereof depending on a temperature thereof; and heating the medium to erase the image recorded thereon, wherein the delivering is carried out using an image processing device containing: a laser light emitting unit; a light scanning unit disposed on a plane onto which laser light emitted from the laser light emitting unit is delivered; a light intensity distribution adjusting unit to change a light intensity distribution of the laser light; and a f(theta) lens to condense the laser light, and wherein energy of the laser light passing through a peripheric portion of the f(theta) lens and traveling onto the medium is lower than energy of the laser light passing through a center portion of the f(theta) lens and traveling onto the medium.