There is a limitation to estimate vitamin B12 intake due to lack of data on vitamin B12 content in many Korean foods. In this study, vitamin B12 content was determined in some soybean or vegetable-fermented foods, edible seaweeds and other frequently consumed foods in Korea by microbioassay using Lactobacillus delbruecki ATCC 7830. The traditional type of Doenjang and Chungkookjang contained 1.85 microgram/100 g and 0.69 microgram/100 g of vitamin B12, respectively, while the factory-type of Doenjang and Chungkookjang contained 0.04-0.86 microgram/100 g and 0.06-0.15 microgram/100 g. Vitamin B12 was not detected in steamed soybeans and Tofu which is a not-fermented soybean product, indicating that vitamin B12 in Doenjang and Chungkookjang might be produced during the fermentation process. The Korean-style soy sauce contained 0.04 microgram vitamin B12/100 mL, but vitamin B12 was not detected in Japanese-style soy sauce and white miso. Commercial Kimchi, a representative Korean vegetable- fermented food, made of Korean cabbage, Yeolmu, or Mustard leaves contained 0.013-0.03 microgram vitamin B12/100 g, while Kimchi without red pepper and fermented fish sauce (White Kimchi) did not. Vitamin B12 content was very high in some edible seaweeds such as laver (66.76 microgram/ 100 g dry weight) and sea lettuce (84.74 microgram/100 g dry weight), and it was 17.12 microgram/100 g of dried small anchovy, 1.07 microgram/100 g of whole egg, and 0.02 microgram/100 g of coffee mix. From these results, it is assumed that Koreans take substantial amount of vitamin B12 from plant-origin foods. And, with these data, we will be able to calculate dietary vitamin B12 content more correctly than before. In conclusion, soybean-fermented foods, Kimchi, laver and sea lettuce are recommendable as good sources of vitamin B12 for vegetarians or Korean elderly on grain and vegetable based diet.