The photocatalytic degradation of a nonionic surfactant, Sanonic SS-90 (polyoxyethylene alkyl ether) which is one of polyoxyethylene nonionic surfactants, in water has been investigated using immobilized titanium dioxide (TiO2) photocatalyst. An external UV irradiation type airlift reactor was used as a photoreactor. The effects of initial nonionic surfactant concentration, intensity of UV light, and concentrations of TiO2 photocatalyst on degradation rate of Sanonic SS-90 were examined. The photocatalytic decomposition of Sanonic SS-90 was assumed to be approximately described by the Langmuir-Hinshelwood kinetics. The rate constant of photocatalytic degradation was found to be proportional to TiO2 surface area and the square root of UV light intensity and independent on the initial concentration of Sanonic SS-90. The evaluated average UV light intensity in the airlift photoreactor was used to determine the rate constants in the Langmuir-Hinshelwood kinetics. It was found that the kinetic model for the degradation by immobilized TiO2 photocatalyst can simulate the experimental results reasonably.