Abstract: According to the New Energy and Industrial Technology Development Organization (NEDO)’s road map in Japan, a polymer electrolyte fuel cell (PEFC) is required to be operated at 90 and 100 ℃ for stationary and mobility application respectively from 2020 to 2025. The PEFC is normally operated from 60 to 80 ℃. If the PEFC is operated at a higher temperature, the following advantages can be expected: (i) enhancement in the electrochemical kinetics of electrodes, (ii) scale-down of the cooling system because of higher temperature difference between the stack of PEFC and the coolant, and (iii) durability enhancement toward CO in lower quality reformed H2. However, we have to consider the following problem at the same time: (i) degradation of the membrane material, (ii) catalyst corrosion, and (iii) gas flows, pressure, temperature, and non-uniform distributions of voltage and current in PEFC. These problems should be resolved in order to commercialize PEFC operating in a relatively high-temperature range. Consequently, it is necessary to analyse heat and mass transfer mechanisms in the PEFC and optimize the components of PEFC to enhance the power generation performance and stability in the high temperature range. This paper reports the investigation result on it.