A photocurable composition comprising (a) a radical-poly- merizabie monomer, (b) a -ketocarbonyl compound and (c) a derivative of mercaptobenzimidazole, mercaptobenzothiazole or mercaptobenzoxazole or an aromatic amine nucleus-substituted with an electron-attractive group has a high photocuring speed at near to normal temperature to give a cured product of excellent physical properties. This composition is valuable as a dental adhesive or resin.