To provide a method for solving the problems involved in treatment technique for removing harmful heavy metal elements by selectively adsorbing cadmium and the like contained in an aquatic product process residue by the help of a chelate-type ion exchange fiber, and a device using this method.

In treating the aquatic product process residue, the process residue is previously cleaned by pure water to remove brine and metals contained in the brine. Next, a solid material is separated from a liquid portion by shear-squeezing the liquid portion from the process residue, and the solid material obtained by the squeezing process is liquefied by the help of protease. After that, centrifugal separation of the solid and liquid and the oil and water is performed, and the obtained separation liquids are brought into contact with the chelate-type ion exchange fiber, respectively to adsorb and remove the harmful heavy metal elements composed mainly of cadmium. The ion exchange fiber has an ion exchange group as a COOH group cleaned previously by a conditioning treatment.