To separate only phosphorus from an alloy containing valuable metals efficiently while maintaining a high recovery rate of the valuable metals such as nickel and cobalt in a valuable metal recovery method for recovering valuable metals from a metal composite containing nickel and cobalt which are valuable metals, such as a waste battery of a lithium ion battery.

The valuable metal recovery method for recovering valuable metals from the metal composite containing nickel and cobalt includes: a melting step in which the metal composite is melted to obtain a molten material; an oxidation step in which the metal composite is subjected to oxidation treatment for the molten material during the melting step or for the metal composite before the melting step; a slag separation step in which slag is separated from the molten material and the alloy containing the valuable metals is recovered; and a dephosphorization step in which phosphorous contained in the alloy is separated. In the dephosphorization step, a lime-containing material is added to the alloy, and then the alloy is oxidized.