The present investigation was carried out to find out the population and the species of yeasts developing in the putrefied marine algae which were gathered at beaches and were made to putrefy in flasks containing fresh sea water at 20℃. The tested marine algae were Chlorophyta (6 species), Phaeophyta (12 spp.) and Rhodophyta (6 spp.). The yeasts developed in following algae, Enteromorpha sp., Ulva pertusa, Codium fragile, Scytosiphon lomentaria, Sargassum hemiphyllum, S. thunbergii, Ishige okamurai, Hizikia fusiforme, Undaria pinnatifida. The yeasts developed in a definite season which varied with the species of algae. The largest number of the yeasts was about 160,000 per 1 g of wet algae. Six species of the yeasts were isolated. They were identified as Torulopsis famata, Candida parapsilosis var. intermedia, C. albicans, Trichosporon behrendii, T. infestans, T. cutaneum. Torulopsis famata and Trichosporon behrendii rapidly grew on wort agar containing 20% NaCl and the yeasts did not alter their salt tolerance after being cultured on wort agar without NaCl for 7 years.