The present invention relates to a high surface hardness transparent resin having excellent scratch resistance, heat resistance and chemical resistance, a glazing material, a protective cover for display devices, an optical lens and a hard coat material comprising the aforesaid resin, and a novel polymerizable monomer which is useful as a raw material of the above-mentioned resin.The monomer is represented by the formula (I) ##STR1## (wherein R is an aliphatic residue having or non having an halogen atom, an oxygen atom, an alicyclic ring, a heterocyclic ring or an aromatic ring, an alicyclic residue, or a heterocyclic residue, n is an integer of 1 to 4, when n=1, X is oxygen or sulfur, when n.gtoreq.2, X's are all oxygen or all sulfur, one X is oxygen while the other X or X's are sulfur, one X is sulfur while the other X or X's are oxygen, or two X's are oxygen while the other X's are sulfur),The aforsaid high surface hardness transparent resin comprises a crosslinked polymer prepared by copolymerizing a monomer (A) represented by the formula (I) and a monomer (B) having, in one molecule, m functional groups of at least one kind selected from the group consisting of CH.sub.2 .dbd.CH--C(O)--O--, CH.sub.2 .dbd.C(CH.sub.3)--C(O)--O--and ##STR2## where (n+m) is an integer of 3 or more.