In this study, a halophilic protease-producing bacterium was isolated from the west seaside mud flats of Korea. The 16S rDNA nucleotide sequences of the isolate showed 99.5% sequence homology with those of Vibrio vulnificus and Vibrio fluvialis; therefore, the isolate was named Vibrio sp. YH-127. Gram staining and the carbohydrate metabolism test results supported the isolate as one from the Vibrio family. Optimum condition for the cell growth and for the protease activity were obtained when the isolate was cultured at 25$^{circ}C$ and pH 7.0, with the salt concentration of the medium similar to that of sea water. Finally, the addition of Mg$^{++}$ ions into medium increases protease activity suggesting that the protease produced by the isolate was a metalloprotease.