The present invention provides a resin composition containing a polyester resin processing, within its molecular structure, a structural unit represented by the following formula (I), and an amino resin: ##STR1## [wherein, R.sup.1 and R.sup.2 are the same or different and each represents a hydrogen atom or lower alkyl, with the proviso that R.sup.1 and R.sup.2 do not simultaneously represent hydrogen atoms]. In addition, the present invention provides a cured resin obtained by means of hardening said resin composition, and a paint containing said resin composition. The aforementioned resin composition provides a cured material that exhibits excellent resistance to hydrolysis, resistance to alkali, and resistance to cissing, and thus is suitable for a paint and the like.