METHOD FOR TREATING ALLOY

Provided is a method for treating an alloy by which nickel and/or cobalt can be selectively isolated from an alloy that contains copper as well as nickel and/or cobalt, in a waste lithium ion battery or the like. The present invention is a method for treating an alloy, by which a solution that contains nickel and/or cobalt is obtained from an alloy that contains copper as well as nickel and/or cobalt, the method including: a leaching step in which a leachate is obtained by subjecting an alloy to an acid-based leaching treatment under conditions in which a sulfurizing agent is also present; a reduction step in which a reduced solution is obtained by subjecting the leachate to a reduction treatment using a reducing agent; and an oxidation/neutralization step in which a solution that contains nickel and/or cobalt is obtained by adding an oxidizing agent and also a neutralizing agent to the reduced solution.