The present invention relates to a cobalt/phosphorus-alumina catalyst in which cobalt is supported as an active component on a phosphorus-alumina support wherein phosphorus is supported on alumina surface. With a bimodal pore structure of pores of relatively different pore sizes, the catalyst provides superior heat- and matter-transfer performance and excellent catalytic reactivity. Especially, when Fischer-Tropsch (F-T) reaction is performed using the catalyst, deactivation by the water produced during the F-T reaction is inhibited and, at the same time, the dispersion and reducing property of cobalt and other active component are improved. Therefore, the cobalt/phosphorus-alumina catalyst for F-T reaction in accordance with the present invention provides good carbon monoxide conversion and stable selectivity for liquid hydrocarbons.