1. A form identification apparatus comprising: storage means for storing ruled line information for a table form; group generation means for obtaining a plurality of possible combinations of ruled lines extracted from an input image and corresponding ruled lines contained in ruled line information of said storage means, and extracting a group of two or more compatible combinations among the plurality of combinations in such a way that no combinations in another group can be contained; and comparison means for comparing the input image with the table form according to information about the combinations contained in one or more extracted groups.