The present invention relates to a transparent resin which has a high surface hardness and which is excellent in 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 above-mentioned resin, and a novel polymerizable monomer represented by the formula (I) useful as a raw material for the high surface hardness transparent resin. ##STR1## wherein R is an aliphatic residue having or not having an oxygen atom, an alicyclic ring, a heterocyclic ring or an aromatic ring, or an alicyclic residue, l is 0 or 1, each of i and j is an integer of 1 or more, and when l=0, i=j=1, when l=1, (i+j) is 4 or less, when j=1, X is oxygen or sulfur, when j.gtoreq.2, all X's are oxygen or sulfur, or one X is oxygen and the other X's are sulfur, or one X is sulfur and the other X's are oxygen.The high surface hardness transparent resin comprises a crosslinked polymer prepared by copolymerizing a monomer (A) represented by the formula (I) as above and a monomer (B) containing one or more 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 t,20