A curable resin includes a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), and a structural unit represented by the following formula (3): ##STR00001## wherein R.sup.1 in the formula (1) is a divalent group having one or more of at least one of an ethylenic double bond and an acetylenic triple bond, and R.sup.2 in the formula (2) is a divalent group having an alicyclic structure.