This study was concerning various physiological activities of agar hydrolysates. All agar hydrolysates showed strong antimicrobial activity against Bacillus subtilis and Bacillus cereus. Also, the agar hydrolysates prepared at the temperature of $110^{circ}C$ or $120^{circ}C$ showed antimicrobial activity against St. aureus and E. coli. Among the agar hydrolysates, several hydrolysates treated with citrate or malate at $110^{circ}C$ or $120^{circ}C$ conditions showed tyrosinase activity inhibition, and their inhibition rates of tyrosinase activity were about 80%. Some tested samples treated with 0.5% organic acid at $100^{circ}C$ or $110^{circ}C$ inhibited the growth of cancer cell. Two agar hydrolysates prepared with 0.5% citrate and lactate at $110^{circ}C$ for $180^{circ}C$ min had relatively high cancer cell growth inhibition among the tested samples. The agar hydrolysates treated with citrate and lactate at $110^{circ}C$ for 180 min obtained the main peaks of six and seven from Sephadex G-15 column chromatography. Among the main peaks, the cancer cell growth inhibition of C-3 and L-3 fractions were higher than that of other fractions.