An attempt has been performed to separate Co(II) and Ni(II) in the sulfate solution by supported liquid membrane containing 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester(HEH(EHP)) as a carrier. The mathematical model for the supported liquid membrane(SLM) of flat type was developed to predict the permeations of metal ions in terms of diffusion at the aqueous boundary layer and organic membrane phase, and the reaction at the aqueous-organic interface. The mathematical model developed for flat SLM showed good agreement with the experimental results.