To provide an image processing method and an image processor which converts a color image into a monochrome image whose colors can be identified.

A work 1 is photographed with a color camera 2, and an image processor 3 operates at least one difference value among the difference values between an R value and a G value, between a B value and the G value and between the R and B values in addition to the R, G and B values of each pixel in a photographed area, sets a color range for regarding a pixel as the same color as a selected pixel about the R, G and B values and the difference value of the pixel, operates difference from the color range of the R, G and B values and the difference value of an optional pixel in the photographed area, respectively changes the difference by scale factors corresponding to the respective difference values, calculates a monochrome image in which the total amount of changed differences is defied as a luminance value and displays the monochrome image on a displaying means 5.