Conditions for ethanol production were evaluated using waste seaweed obtained from Gwangalli beach, Busan, Korea, after strong winds on January 15, 2015. Eleven types of seaweed were identified, and the proportions of red, brown, and green seaweed wastes were 26, 46, and 28%, respectively. Optimal pretreatment conditions were determined as 8% slurry content, 286 mM H2SO4 for 90 min at 121 A degrees C. Enzymatic saccharification with 16 units/mL Celluclast 1.5L and Viscozyme L mixture at 45 A degrees C for 48 h was carried out as optimal condition. A maximum monosaccharide concentration of 30.2 g/L was obtained and used to produce ethanol. Fermentation was performed with single or mixed yeasts of non-adapted and adapted Saccharomyces cerevisiae KCTC 1126 and Pichia angophorae KCTC 17574 to galactose and mannitol, respectively. The maximum ethanol concentration and yield of 13.5 g/L and Y-EtOH of 0.45 were obtained using co-culture of adapted S. cerevisiae and P. angophorae.