Leaching method for lithium ion battery scrap and method for recovering metal from lithium ion battery scrap

Provided are a leaching method for lithium ion battery scrap that makes it possible to effectively reduce treatment costs and a method for recovering metal from lithium ion battery scrap. This leaching method for lithium ion battery scrap includes a metal leaching step in which when subjecting lithium ion battery scrap that contains nickel and/or cobalt to leaching in an acidic solution, the scrap is added together with at least one of elemental manganese and/or iron that is not included in the scrap, a compound of manganese and/or iron, and/or a solution containing manganese and/or iron metal ions to the acidic solution so that manganese and/or iron metal ions are present within the acidic solution, the nickel and/or cobalt included in the scrap are subsequently brought into contact with the manganese and/or iron metal ions within the acidic solution in which the manganese and/or iron metal ions are present, and the nickel and/or cobalt are leached as a result.