[Object] To provide a composite body in which the Cr diffusion can be sufficiently reduced and conductivity is good, a collector member, a fuel battery cell device, and a fuel battery device. [Solution] The composite body includes a substrate 200 containin...

A proton-conductive inorganic thin film including an inorganic proton conductor, a method of forming the proton-conductive inorganic thin film, and a fuel cell including the proton-conductive inorganic thin film as an electrolyte membrane.