1. An apparatus for converting a monochrome image to an estimated color image so as to display the estimated color image, comprising: edge image generating means for detecting edges in the monochrome image to generate an edge image indicative of the detected edges only; four-division means for dividing the edge image into four areas, an upper area, a lower area, a left area and a right area with two cross lines; object determining means for determining an object forming the edge image in each of the four areas; and estimated color image making means for assigning a color to the object determined by the object determining means for each of the four areas in order to make the estimated color image.