For the removal of catechin from green-tea extracts, N-vinylpyrrolidone-grafted fiber was prepared by radiation-induced graft polymerization of N-vinylpyrrolidone (NVP) onto a commercially available 6-nylon fiber. The adsorption isotherm of the NVP fiber with a density of 3.9 mmol/g for catechin in green-tea extracts was well correlated by Langmuir-type equation. The maximum adsorption capacity and adsorption constant were 0.23 mmol/g and 13 L/mmol, respectively. Catechin adsorbed onto the NVP fiber was eluted completely with 0.1 M NaOH. In the second to fourth cycles of adsorption and elution, the amount of catechin adsorbed onto the NVP fiber remained almost constant.