Abstract: A cyanoethyl group-containing graft polymer comprising a hydrocarbon polymer backbone comprising butadiene units, to which a cyanoethylated (meth)acrylate monomer of the formula:CH.sub.2 .dbd.CR.sub.1 --COO--R.sub.2 --(OCH.sub.2 CH.sub.2 CN).sub.min which R.sub.1 is a hydrogen atom or a methyl group; R.sub.2 is a residue derived from a (m+1)-valent polyhydroxyl compound by the removal of all the hydroxyl groups; and m is an integer of at least 1, which is useful as a binder resin for positive and negative electrodes of lithium ion secondary batteries and for organic dispersion type electroluminescent device.