A vinylated alkoxyamine represented by general formula (1) is produced by a process comprising the step of heating divinylbenzene together with a nitroxide compound and an organic peroxide to the heat decomposition temperature of the organic peroxide. In said formula, R1 represents aryl or R2O; R2 represents C¿1-12?, linear or branched (cyclo)alkyl; and R?3 and R4¿ each represents C¿4-6? tertiary alkyl or R?3¿ is bonded to R4 to form a C¿8-16? cyclic structure which is unsubsituted or substituted by any of aklyl, oxo, hydroxy, acyloxy, and alkoxy. A polymeric free-radical polymerization initiator having a pendant alkoxyamine group can be used to produce a graft polymer.