Lipase from Candida cylindracea or Rhizopus was immobilized in gel beads prepared by copolymerization of N-isopropylacrylamide, H-N＇-methylenebisacrylamide, and acrylamide. The hydrolysis reaction of castor oil was carried out at 37 degrees C by using immobilized lipase or free lipase. The optimal condition of immobilization of lipase and the productivity of ricinoleic acid is investigated. It is found that thermal inactivation of enzyme was suppressed and the formation of by-products such as estolide decreases by immobilization into the gel compared with free lipase.