PURPOSE: To extract routes including terminal points by erasing terminal points and characters in a drawing in which symbols, characters and routes are mixed, extracting only symbol data, comparing the symbol data with the original drawing and erasing the symbol data.

CONSTITUTION: A picture memory 1 of an original data containing symbols, routes and characters is thinned by a thinning circuit 2. Terminal points are erased 3 from the thinned picture and further characters are removed. Then, a picture 5 obtained by cutting out 5 symbols is compared 6 with the thinned picture 2 and subtracted to leave only routes containing terminal points. By this way, symbols and routes can be extracted easily from figures in which symbols, routes and characters are mixed such as flow charts, logical operation circuits etc.