The present study was designed to investigate whether traditional Korean fermented soybean paste(doen-jang) and soybean extracts have inhibitory effects on the growth of KB cell, an oral epithelioid cancer cell. When KB cell ATCC CCL-17 was cultivated for 48 flours with the addition of 0.5% of the five types or doen-jang extract, the growth of KB cell was inhibited by all types of extract, and ethyl acetate extract showed the highest inhibitory effect. In case of soybean extract, all types of extract also showed KB cell inhibitory effects, however, generally less than those of doen-jang extract. When ethyl acetate extract of doen-jang was added in different concentrations and KB cell was cultivated for 24 hours and 45 hours, strong inhibitory effect began to appear from the concentration of 1.25 mg/ml. Although soybean extract showed such a tendency, its effect was lower than that of doen-jang extract. These results indicate that doen-jang extract has inhibitory effect against KB cell, and particularly ethyl acetate extract has the highest effect. The effect of doen-jang extract might be possibly enhanced by the fermentation of soybeans. It is assumed that doen-jang extract may be used to develop nontoxic medicines for preventing and treating oral diseases.