The present invention relates to novel 1-azaxanthone-3-carboxylic acid and its derivatives usable for effective medicines for the treatment of allergic diseases, which are shown by the following formula (I) ##STR1## wherein R.sub.1 is hydrogen, alkyl, phenyl, carboxyl, hydroxyl, alkoxy or amino group which may be unsubstituted or substituted by one alkyl, m is 0, 1 or 2 and R.sub.2 is alkyl, alkoxy, halogen, nitro, hydroxy, carboxyl, butadienylene (--CH.dbd.CH--CH.dbd.CH--) which forms a benzene ring with any adjacent carbon atoms or amino group which may be unsubstituted or substituted by at least one alkyl, and their physiologically acceptable salts.