Phaeodactylum tricornutum is a marine diatom belonging to the Bacillariophyceae class of algae and contains 7-35 wt% of lipids in the forms of myristic acid, eicosapentaenic acid and others. Due to the high growth rate, P. tricornutum attracts interest as a substitute for the fossil hydrocarbons of petroleum as an energy source and as a way of carbon dioxide fixation. In this study, R tricornuturn was cultivated in batch operation in artificial seawater with granular activated carbon (GAC) and activated carbon fiber (ACF) as the adherent material. The growth rate of P. tricornutum was increased with the addition of ACF, compared to the case of GAC and no culture adherent material used. We examined the optimum culture conditions of P. tricornutum in terms of the biomass concentration and growth rate, in terms of the quantity of ACF addition and concentration of carbon dioxide. It was found from the experimental investigation that the optimum operating condition of fixation of carbon dioxide concentration was 5-10% and downward in the air.