An electrolyte layer (121) and a hydrogen-permeable metal layer (122) are fitted in a fitting portion (131) of a low thermal expansion member (130), and a cathode electrode (110) is provided on the electrolyte layer (121). Gas separators (100, 150) are provided such that a low thermal expansion member (130) is held between the gas separators (100, 150). Since the low thermal expansion member (130) is made of metal which has a thermal expansion coefficient lower than that of the hydrogen-permeable metal layer (122), thermal expansion of the hydrogen-permeable metal layer (122) can be suppressed. Accordingly, it is possible to reduce shear stress applied to an interface between the electrolyte layer (121) and the hydrogen-permeable metal layer (122) due to the thermal expansion. It is possible to suppress separation of the electrolyte layer (121) from the hydrogen-permeable metal layer (122) and occurrence of a crack in the electrolyte layer (121).