Disclosed herein is a porous membrane having an immobilized enzyme wherein the enzyme is immobilized within pores which are three-dimensionally connected to each other. The porous membrane having the immobilized enzyme is three-dimensionally crosslinked in a molecular level wherein nanopores of 5 to 100 nm are interconnected, so that the immobilized enzyme may be in contact with a reactant in all directions, and the reaction solution may be easily diffused, thereby proceeding with the catalytic reaction fast and conveniently without deterioration of material transport.