Film- and continuous-phase mass transfer in liquid-liquid system was studied using a cocurrent laminar wetted-wall column of a modified form. The film-phase mass transfer coefficients were measured by dissolution of n-butanol, ethyl acetate and cyclohexanone in water, and the continuous-phase mass transfer coefficients measured by the transfer of I₂ disappeared by the instantaneous irreversible reaction with Na₂S₂O₃ in the aqueous film-phase. These coefficients could be analyzed by the penetration theory and were in good agreement with Beek-Bakker model.