Nine species of edible seaweed [green laver (Monostroma nitidium) and sea staghorn ( Codium fragile) of green algae; sea mustard (Undaria pinnatifida), seaweed fusiforme(Hizikia fusiforme), gulf weed (Sargassum fulvellium), and sea tangle (Laminaria japonica) of brown algae; seaweed dilatata (Halimeniopsis dilatata), seaweed furcata (Gloiopeltis furcata), and laver (Porphyra tenera) of red algae] collected from Kijang, Chungmu, and Yosu in Korea, were examined and compared on their chemical and mineral composition depending on their harvesting season. Crude protein $(Npm6.25)$ showed about $45\%$ on moisture free basis (the contents of every components described below are shown as moisture free basis) for laver and $30\%$ for green laver collected from ever seasons and sites. Sea tangle showed the highest content in crude lipid $(10\%)$ among brown seaweeds and green laver had $6\%$ of crude lipid regardless their habitats. Ash and carbohydrate in sea staghorn hold about $90\%$ of total solids but those levels were only $50\%$ in laver. The relationship between ash and carbohydrate content showed a tendency with reverse correlation. Mineral compositions were examined on green laver, sea mustard, and seaweed furcata collected from Kijang. Sodium was eminent element (1,798-7,334mg/l00g) followed by potassium. Magnesium and calcium content were low level compared with sodium and potassium. As a micro-element iron was appraised the highest status (165-330mg/100g) in green laver, however, iron in sea mustard and seaweed furcata was comparatively low amount (2.7-47.4mg/100g). The level of zinc was also comparatively high and that was varied on habitats. In conclusion, chemical compositions of these algae were distinctively varied on species and habitats, and mineral compositions were notably changed by the harvesting season.