Gelatin hardening agents represented by the following formulae (I) or (II):a.sub.1 --b.sub.1 --r.sub.1 --b.sub.2).sub.n A.sub.2 (I)(a.sub.1 --b.sub.1).sub.3 r.sub.2 (ii)wherein A.sub.1 and A.sub.2 each represents an azole group which is linked to B.sub.1 or B.sub.2 by a nitrogen atom, wherein the azole group is a 5-membered ring having 2 or more nitrogen atoms which has a conjugated system and which may include a condensed ring, B.sub.1 and B.sub.2 each represents ##STR1## R.sub.1 represents a divalent group, R.sub.2 represents a trivalent group, and n represents 0 or 1.