Antimicrobial activities of grape seed ethanol extract and its serial solvent fractions were investigated against various food poisoning microorganisms. The grape seed ethanol extract showed dose dependant antimicrobial activity against Bacillus subtilis ATCC 9372 or Staphylococcus aureus ATCC 6538, whereas had limited effect on Pseudomonas aeruginosa IFO 3080, Salmonella enteritidis IFO 3313 and Escherichia coli ATCC 25922. Ethylacetate and butanol fractions ameng the serial solvent fractions of grape seed ethanol extract contained the catechin at the levels of 35.7 mg/g and 20.2 mg/g, respectively. Nevertheless, the butanol fraction of grape seed ethanol extract showed intense antimicrobial activity compared with the ethylacetate fraction on all microorganisms tested. It was found that the butanol fraction was mainly composed of oligomeric or polymeric polyphenols such as condensed tannins by the fractionation on C l8 cartridge according to the difference in the degree of polymerization. Therefore, it seems that the antimicrobial activity of grape seed ethanol extract is related to the degree of polymerization of proanthocyanidin as well as the total content of flavan-3-ol composing the proanthocyanidin.