The objective of this paper is to observe water production behavior inside of the cell and to analyze its effect on current distributions over the reaction area. A fuel cell was made to allow direct observation of the phenomena in cathode side and local current density measurement in anode side. The experimental results showed that the cell performance and current density distribution of air operation is strongly affected by the condensed water compared with those of O_2 operation, although the drainage of air operation is superior. It was also shown from the comparison experiments of separator type that the serpentine separator has advantage to drain away the condensed water because of its high gas velocity, and may make gas paths deep in the gas diffusion layer. On the other hand, when the condensed water is drained efficiently, the straight separator can realize homogeneous current density distribution because of its shorter channel paths.