Abstract: A process for concentrating and recovering a surfactant aqueous solution, by evaporating and concentrating a surfactant aqueous solution containing a gasifiable surfactant and an aqueous solvent to increase the concentration of the surfactant, which comprises storing the surfactant aqueous solution in an evaporator 12; adjusting the temperature of the surfactant aqueous solution in the evaporator 12 to be lower than the boiling point of the aqueous solvent under the pressure in the evaporator 12; withdrawing a part of the surfactant aqueous solution from the evaporator 12, superheating it by a superheater 14 under conditions that all the surfactant and the aqueous solvent are formed into an annular flow or an annular mist flow, and spraying it from a nozzle 32 having a shape such that the outlet side first narrows and then widens outward, into the evaporator 12; and evaporating and removing the aqueous solvent.