This study was conducted to figure out the nutritional nature of seafoods categorized according to the medicinal effects and the usages introduced in Lim-Won-Sib-Rheuk.-Ji, one of the well-known encyclopedias published during the Chosun Dynasty. They were compared with those introduced in other cooking books in order to find out how they were used in the diet of real-life. The seafoods of the book were first categorized into the fish 20, the mollusk 5, the crustacea 4, and the shellfish 7, and reptile according to the biological taxonomy, and then each one was reviewed in terms of the taste and the food-nature. Generally, the fishes had the sweet taste; the crustacea and the shellfish the salty or sour in addition to the sweet taste; none of them were bitter or hot. Most of them had the mild nature; seven of them were regarded as warm; four as cool; one as cold from the standpoint of the traditional medicine. The food-nature of seafoods was closely related with the medicinal effects on the human body. These seafoods were characteristically used in daily dietary life as well as the medical applications; used as the side-dishes rather than the main-dishes. The cooking methods of boiling, steaming, and baking were preferred to drying and stewing. The preservation methods favored were the fermentation, drying and salting. These cooking and preservation methods were believed to reflect the nature of the seafoods to manifest the medicinal effects.