A method for removing radioactive cesium and/or iodine from a radioactive substance in liquid and/or a solid matter using a hydrophilic resin composition comprising a hydrophilic resin and a metal ferrocyanide compound, wherein the hydrophilic resin includes at least one hydrophilic resin selected from the group consisting of a hydrophilic polyurethane resin, a hydrophilic polyurea resin, and a hydrophilic polyurethane-polyurea resin each having at least a hydrophilic segment, and a metal ferrocyanide compound is dispersed in the hydrophilic resin composition in a ratio of at least 1 to 200 mass parts relative to 100 mass parts of the hydrophilic resin.