Butyric acid fermentation by Clostridium tyrobutyricum ATCC 25755 using glucose or brown algae as a carbon source was carried out. Initially, different fermentation modes (batch, fed-batch, and semi-continuous) at pH 6 and $37^{circ}C$were compared using a model medium containing glucose as a carbon source. By feeding the whole medium containing 40 ~ 50 and 30 g/L of glucose into the fed-batch and semi-continuous fermentations, very similar butyrate yields (0.274 and 0.252 g butyrate/g glucose, respectively) and productivities (0.362 and 0.355 g/L/h, respectively) were achieved. The highest butyrate concentration was about 50 g/L, which was observed in the fed-batch fermentation with whole medium feeding. However, semi-continuous fermentation sustained a longer fermentation cycle than the fed-batch fermentation due to end-product and metabolic waste inhibition. The established conditions were then applied to the fermentation using brown algae, Laminaria japonica and Undaria pinnatifida, as substrates for butyric acid fermentation. To hydrolyze brown algae, 7.5 ~ 10% (w/v) dried brown algae powder was suspended in 1% (w/v) NaOH or 0.5 ~ 2.5% (w/v) $H_2SO_4$ and then autoclaved at $121^{circ}C$ for 30 ~ 90 min. The resulting butyrate concentration was about 11 g/L, which was produced from 100 g/L of L. japonica autoclaved for 60 min in 1.5% $H_2SO_4$ acid solution.