The present invention is concerned with a vinyl polymer having at least one group of the general formula (1) permolecule at the molecular chain terminus. --Z--R--CR.sup.1.dbd.CR.sup.2R.sup.3 (1) wherein Z represents an oxygen atom, a sulfur atom, a group of the formula NR', R' represents a univalent hydrocarbon group containing 1 to 20 carbon atoms, or a bivalent organic group containing 1 to 20 carbon atoms, and R represents a carbonyl group, a direct bond or a bivalent organic group containing 1 to 20 carbon atoms; R.sup.1 and R.sup.2 are the same or different and each represents a hydrogen atom or a univalent organic group containing 1 to 20 carbon atoms, and R.sup.3 represents an organic group containing 1 to 20 carbon atoms.The present invention is further concerned with a curable composition comprising the above vinyl polymer.