It was investigated the mass transfer rate for extraction and stripping of Cr(VI) ion from aqueous solution into the extractant and stripping the ion from the extractant to NaOH solution by using the hydrophobic hollow fiber membrane module. To determine the rate controlling step for mass transfer in the module, we also examined the effect of inside and outside flow rates of the fibers on the overall mass transfer coefficients. For the systems with high distribution ratio, we note that mass transfer rate was independent of outside flow rates, but inside flow rates had a great influence on the mass transfer rate.