PURPOSE: To precipitate platinium group elements in excellent yield by treating a waste catalyst in which the platinium group elements are contained as the catalyst with concd. sulfuric acid, thereafter extracting the platinium group elements with dil. aqua regia to separate them from the carrier and adding alkaline boron hydride to the extracted soln.

CONSTITUTION: A waste catalyst deposited with platinium group elements such as Pt, Pd, Rh, Ru, Os and Ir on a carrier is mixed with concd. sulfuric acid of ≥90% concn. and heated at 60W100°C to disintegrate the waste catalyst. Then, water is added thereto and the mixture is filtered and dil. aqua regia wherein HNO3:HCl:H2O is (1:3:4)W(1:4:4) is added to the filtered residue to dissolve and extract the platinium group elements contained in the residue. The filtrate is neutralized with aq. NaOH soln. and furthermore regulated to >11pH. An alkaline boron hydride such as sodium boron hydride is added thereto and the platinium group elements contained in the extracted soln. are reduced, deposited and precipitated and thereafter filtered to recover the platinium group elements.