In the conventional phosphoric acid fuel cell, the filter type or scrubber type phosphoric acid capture system is installed to prevent the scattering of phosphoric acid to the downstream of the cell. However, these phosphoric acid capture systems have such disadvantage that the decrease in capture efficiency and the possibility of operation stop due to the increase in pressure drop in the capture system is likely to take place. This invention solves the problem. The phosphoric acid capture system which employs the rotation collision action for capturing the mist to make it collide to the wall surface by applying the centrifugal force is installed on the exhaust gas line of the fuel cell. A cooling system which utilizes the air or the oxidizer to be supplied to the fuel cell as a cooling medium from the blower is installed on the upper stream of the said phosphoric acid capture system to condense the phosphoric acid mist in the exhaust gas by cooling down and to capture it by the capture system. With this system, the efficiently capturing the phosphoric acid can be achieved. 6 figs.