A photocurable and thermosetting resin composition comprises (A) an actinic energy ray-curable resin having at least one structure represented by the following general formula (1), (B) a-polymerization initiator, (C) a diluent, and (D) a polyfunctional oxetane compound. The actinic energy ray-curable resin mentioned above can be produced by causing the reaction of (a) a polyfunctional oxetane compound with (b) an unsaturated monocarboxylic acid and the subsequent reaction of (c) a polybasic acid anhydride with a primary hydroxyl group of the resultant modified oxetane resin (a'). ##STR00001## wherein R.sup.1 represents a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, R.sup.2, R.sup.3 and R.sup.4 independently represent a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an aryl group, an aralkyl group, a cyano group, a fluorine atom, or a furyl group, and X represents a polybasic acid anhydride residue.