1. A method for processing a contrast picture image of a semiconductor element comprising: a color grade number reducing processing that automatically reduces a number of color grades of said contrast picture image of the semiconductor element, obtained from a device for analysis, in keeping with the contrast of said contrast picture image; an interconnect contrast extraction processing that classifies pixels contained in said contrast picture image, whose number of color grades has been reduced, in accordance with a preset contrast threshold value as reference, to extract an interconnect pattern fractionated into a plurality of number of contrasts, wherein said interconnect contrast extraction processing includes: (1) turning said contrast image, whose number of color grades has been reduced, into a bi-level image, using a preset first contrast threshold value as reference, to extract an interconnect pattern of a first contrast level; and (2) turning a contrast image, obtained after excluding the interconnect pattern already extracted in the color-grade-number-reduced contrast image, into another bi-level image, using a K'th contrast threshold value out of an N-number of the contrast threshold values as reference, where N is the number of said contrast threshold values and is an integer not less than 2, to extract an interconnect pattern of the K'th contrast level; the sequence of operations of turning the contrast images into the bi-level images and extracting the interconnect patterns being repeated as the value of K is incremented by 1 from K=2 until K=N each time, where K is an integer; whereby the interconnect patterns fractionated into N levels of contrast is extracted; and a shift processing that removes noise contained in a contour portion of said interconnect pattern by shifting said contour portion; whereby an interconnect pattern contained in said contrast image of said semiconductor element obtained from said device for analysis is fractionated into a plurality of preset contrasts to be extracted.