A resin composition for molding having excellent heat resistance, hardness, cost-effectiveness, and biodegradability is provided by using an amorphous resin material component extracted from plant-derived wood. The resin composition is a hemicellulose monomer obtained by applying a methacrylation reaction or acrylation reaction to a hemicellulose or hemicellulose derivative and has a molecular structure in which a methacrylic group or acryloyl group is bonded to the hemicellulose or hemicellulose derivative. This hemicellulose monomer has excellent injection moldability.