A photopolymerizable composition is described comprising (1) an addition-polymerizable compound having at least one ethylenically unsaturated double bond, (2) a photopolymerization initiator, and (3) a post-exposure polymerization inhibitor compound including a thioureylene group, such as a compound selected from the group consisting of thiourea and thiourea derivatives represented by the general formula (I), thiosemicarbazide and thiosemicarbazide derivatives represented by the general formula (II), and thiosemicarbazone derivatives represented by the general formula (III): ##STR1## wherein: R.sup.1 and R.sup.2, which may be the same or different each represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, a substituted alkyl group having from 1 to 6 carbon atoms, a phenyl group, a naphthyl group, a substituted phenyl group or a monovalent group derived from an O-, S- or N-containing 5- or 6-member heterocyclic nucleus,R.sup.3 represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, a substituted alkyl group having from 1 to 6 carbon atoms, a phenyl group, a naphgroup or a substituted phenyl group,R.sup.4 represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms,R.sup.5 represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, a phenyl group, a naphthyl group, a monovalent group derived from an 0-, N- or S-containing 5- or 6-member heterocyclic nucleus, an alkylcarbonyl group having from 2 to 7 carbon atoms or a benzoyl group,R.sup.6 represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, a phenyl group or a naphthyl group,R.sup.7 represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms, andR.sup.8 represents an alkyl group having from 1 to 6 carbon atoms, a phenyl group, a naphthyl group or a substituted phenyl group.