A radical copolymerization behavior of limonene oxide and methylacrylate was investigated, by which a partially biobased polymer-bearing reactive epoxy groups in the side chains was obtained in 43 % yield in the maximum. Degree of LO incorporation into the copolymer was determined to be 34–37 % when 5.0 mol % of 2,2′-azobis(isobutyronitrile) was employed, despite initial feed ratios. Reactivity of the epoxy groups in the side chains was investigated by two different methods. One is ring-opening of the epoxy groups with benzyl thiol, giving the corresponding polymer with β-hydroxyl sulfide moieties in 95 % yield. Another one is hydrolyzation of the epoxy groups in HCl aqueous solution at room temperature, providing a quantitative formation of the dihydroxyl groups in the side chains.