The present invention provides an expression vector comprising genes encoding OmpF of E. coli and a desired protein, E.coli transformed with the expression vector, and a method for extracellular production of desired proteins by employing the same. The recombinant expression vector of the invention comprises an ampicillin-resistance gene, the OmpF promoter and the OmpF gene. In accordance with the invention, a desired protein can be produced extracellularly by a simpler method than conventional methods such that: secretory production of OmpF fusion protein begins simultaneously with growth of the cells through constitutive expression employing an OmpF promoter, and as the concentration of cells increases, the amount of secretory production of the protein also increases continuously. Therefore, desired proteins can be produced in large quantities by a high concentration culture of cells.