Decellularization of tissue by means of an amphipathic solvent a well-established practice. However, situations exist where the provision of enhanced decellularization is preferred. There is a demand for treating methods for coping with such situations. Thus, it is intended to provide a method for enhancing decellularization. The method comprises not only the immersing of a tissue in a solution containing an amphiphilic molecule in non-micellar form (for example, 1,2-epoxide polymer) but also performing a radical reaction (for example, treatment selected from the group consisting of exposure to gamma-ray irradiation, ultraviolet irradiation, a free radical supply source, ultrasonication, electron beam irradiation, and X-ray irradiation).