The methane generation system according to the present invention includes a methane generation unit including an electrolysis device that electrolyzes water to obtain hydrogen and a methane reactor that obtains a fuel gas containing methane by a methanation reaction using the hydrogen; a reformer that reforms the fuel gas to obtain a reformed gas; a fuel cell that generates electricity by a reaction of obtaining a product gas from the reformed gas and an oxygen-containing gas; a recovery device that separates a recovery gas containing carbon dioxide from return fluid which is a part of the product gas; and a circulation path through which the recovery gas is guided to the methane generation unit.
