PURPOSE: To extraction Ga ions with high efficiency without changing the qualities of the source solution by extracting Ga ions from a basic solution with an org. solvent containing a specified extractor and a specified extraction accelerator.

CONSTITUTION: The Ga ion-contg. basic solution (A) is separated from the production process of alumina. The metal extractor (B) is prepared by compounding one or more kinds of substd. hydroxy quinoline expressed by formula I. (R1-6 represent H or straight chain alkyl groups. R1-6 may be same or different from one another but it is not allowed that all of them are hydrogen). Then esters of formulae II-IV (wherein R10, R14, R16 are straight chain alkyl groups of ≥11C) derived from straight chain paraffin hydrocarbons of ≥12C are mixed to prepare the extraction accelerator (C) which is insoluble or hardly soluble in water and shows non-ion surface activity. Then a compd. (D) having a different chelate coordination from (C) component and/or (B) component is mixed with (C) component to prepare an org. solvent (E). Ga ions are extracted from (A) component with (E) component, and the obtd. org. phase is subjected to reverse extraction with a solution of mineral acid containing HCl, etc., to extract Ga ions into a water phase.