The authors have synthesized the amphiphilic polymer, poly [2-methacryloyloxyethyl phosphorylcholine (MPC) -co-butylmethacrylate (BMA)], and its unique properties were clarified in comparison with commercial moisturizing agents. In skin care studies, measurement of water holding capacity showed 0.2wt% of the poly (MPC-co-BMA) to hold water equally or more than sodium hyaluronate. Using poly (MPC-co-BMA) lotion, 1.0wt% of the poly (MPC-co-BMA) prevented trans epidermal water loss for at least 7 days. Increase in visco-elasticity using 1.0wt% of the poly (MPC-co-BMA) was the same as that by sodium hyaluronate, and equall or greater than that of glycerol. Stratum corneum cells were significantly removed from elbow by tape stripping before treatment, in contrast to 1.0wt% poly (MPC-co-BMA) containing cream for 14 days. Poly (MPC-co-BMA) showed decreased surface electric resistance on using 1.0wt% of poly (MPC-co-BMA). Treatment of hair with poly (MPC-co-BMA) made it smooth and increased its strength and water content. This compound protects hair and skin from damage, rather than having curing effect.