An improved approximate solution of the facilitation factors in facilitated transport has been developed for the case where a reversible reaction A(permeate) + B(carrier) reversible arrow C(complex) occurs in the membrane. It was confirmed that the facilitation factors calculated by the present approximation method agree with the results which had been obtained previously by numerical integration of the governing differential equations over the entire range from the physical diffusion region to the chemical equilibrium region for the case of both equal and unequal carrier and complex diffusivities and also for the case of nonzero downstream permeate concentration. Furthermore, the behavior of the concentration profiles in the membrane could be explained by the proposed approximate analysis.