The present invention relates to a process for preparing a hard transparent resin comprising polymerizing a monomer (A) having both a functional group of the following formula (I): ##STR1## wherein X is selected from the group consisting of an oxygen atom and a sulfur atom,and a functional group selected from the group consisting of a functional group of the formula (II):CH.sub.2 CR--COO-- (II)wherein R is selected from the group consisting of hydrogen and methyl group,and a functional group of the formula (III): ##STR2## The invention also provides a process for preparing a transparent resin comprising copolymerizing monomer (A) with a monomer (B) having at least one functional group selected from the group consisting ofCH.sub.2 .dbd.CHCOO--,CH.sub.2 .dbd.C(CH.sub.3)--COO--, and ##STR3## This resin can be suitably used as a glazing material, and in the manufacture of optical lenses, optical information recording medium substrates, etc. It has a crosslinked structure, high surface hardness, and may be easily polymerized.