A diamine compound represented by the formula (1): ##STR00001## wherein R.sup.1 is a trivalent organic group, each of X.sup.1 and X.sup.2 is a bivalent organic group, X.sup.3 is an alkyl or fluoroalkyl group having from 1 to 22 carbon atoms, or a cyclic substituent selected from aromatic rings, aliphatic rings, heterocyclic rings and their substituted groups, and n is an integer of from 2 to 5. And, a polyimide precursor and a polyimide synthesized by using the diamine compound; and a treating agent for liquid crystal alignment containing the polyimide precursor and/or the polyimide.