Recently Vibrio sp. are the most frequently isolated microorganism, which causing food poisoning. We investigated the detection of toxin genes and effect of chitosan to toxin genes with PCR. Thirty strains of Vibrio sp. were isolated from sea water and sea products through biological and biochemical tests. Out of 30 strains, 8 were identified as V. parahemolyticus, 7 as V. mimcus, 6 as V. damsela, 5 as V. vulnificus, 4 as V. alginoyticus. In detection of ctx, tdh, and t고 as food poisoning-causing toxin genes, ctx from 7 strains, trh from 4 strains and tdh from 6 strains were detected. Among toxin genes detected strains, we selected V. vulnificus-2 V. damsela-1 and V. parahemolyticus-7. As adding chitosan solution to PCR product of 3 strains, the amplified DNA bands were not detected over 450$mu extrm{g}$/$mell$ concentrantion of chitosan. Over the result, chitosan is thought to influence the detection of toxin gene.