A strain producing eggshell membrane protease (ESM protease) was isolated from the soil and identified as Pseudomonas aeruginosa. The enzyme isolated from the fermentation liquid of this strain and purified by ammonium sulfate precipitation, quadratic anion-exchange chromatography exhibited eggshell membrane degrading activity of 304.5 U/mg. By SDS-PAGE, the protein molecular mass is 32 kD. The N-terminal amino acid sequence of this protease is: Ala, Glu, Ala, Gly, Gly, Val, Ala, Gly, Lys, Glu, Asp, Ala, Ala, Glu, Leu.