Solid electrolyte, production method thereof, and all-solid-state battery

A solid electrolyte having high ion conductivity and high electrochemical stability is provided. This solid electrolyte 30 contains a carbon material 32 and a hydride-base solid electrolyte material 31, wherein the volumetric ratio of the carbon material 32, which contains either fullerenes or higher fullerenes, and the hydride-base solid electrolyte material 31, which contains a complex hydride, is in the range of 1:99 to 10:90.