Prunus cerasus (Japanese cherry blossom: Sakura) was liquefied in polyethylene glycol—glycerol co-solvent with sulfuric acid (H 2 SO 4 ) as a catalyst. The liquefied wood was blended with poly-4,4′-diphenylmethane diisocyanate to prepare polyurethane (PU) resin. In addition, inorganic–organic hybrid biodegradable polyurethane resin was prepared by adding tetraethoxysilane into liquefied-wood-derived polyurethane. It was found that the thermal stability of liquefied-wood-derived polyurethane is better than general polyurethane. Furthermore, it was ensured that Si was introduced in PU at a molecular level, while maintaining the urethane structure.