An apparatus of producing methane from a CO 2 -containing gas, comprising: at least two reactors which are provided with a CO 2 storage-reduction catalyst in which a component having a methanation catalytic ability and a component having a CO 2 storage capacity are supported on a catalytic support; at least one reactor which is provided with a methanation catalyst in which a methanation catalytic component is supported on a porous catalytic support; at least one means for supplying purge gas; and at least one means for supplying reducing gas, wherein two or more of the reactors provided with the CO 2 storage-reduction catalyst are connected in parallel, the at least one means for supplying purge gas selected from the group consisting of noble gases and inert gases and the means for supplying reducing gas are disposed upstream of the reactors provided with the CO 2 storage-reduction catalyst on gas flow paths, the reactor provided with the methanation catalyst is disposed downstream of the reactors provided with the CO 2 storage-reduction catalyst on the gas flow paths, a gas supply line for supplying the CO 2 -containing gas and the means for supplying reducing gas are connected to each one of the reactors provided with the CO 2 storage-reduction catalyst such that the CO 2 -containing gas and the reducing gas are separately and independently supplied to the each one of the reactors provided with the CO 2 storage-reduction catalyst, a gas outlet of each one of the reactors provided with the CO 2 storage-reduction catalyst is connected to a gas inlet of at least one different reactor provided with the CO 2 storage-reduction catalyst, other than the one reactor, via a purge gas recirculation line which supplies the purge gas containing CO 2 emitted from the gas outlet of the one reactor into the gas inlet of the different reactor, each one of the reactors provided with the CO 2 storage-reduction catalyst has a feature capable of alternately carrying out the storing of CO 2 and the reducing of CO 2, and at least one of the reactors provided with the CO 2 storage-reduction catalyst is configured for carrying out the storage of CO 2 and simultaneously a remaining reactor provided with the CO 2 storage-reduction catalyst is configured for carrying out the reducing of CO 2. at least two reactors which are provided with a CO 2 storage-reduction catalyst in which a component having a methanation catalytic ability and a component having a CO 2 storage capacity are supported on a catalytic support; at least one reactor which is provided with a methanation catalyst in which a methanation catalytic component is supported on a porous catalytic support; at least one means for supplying purge gas; and at least one means for supplying reducing gas, wherein two or more of the reactors provided with the CO 2 storage-reduction catalyst are connected in parallel, the at least one means for supplying purge gas selected from the group consisting of noble gases and inert gases and the means for supplying reducing gas are disposed upstream of the reactors provided with the CO 2 storage-reduction catalyst on gas flow paths, the reactor provided with the methanation catalyst is disposed downstream of the reactors provided with the CO 2 storage-reduction catalyst on the gas flow paths, a gas supply line for supplying the CO 2 -containing gas and the means for supplying reducing gas are connected to each one of the reactors provided with the CO 2 storage-reduction catalyst such that the CO 2 -containing gas and the reducing gas are separately and independently supplied to the each one of the reactors provided with the CO 2 storage-reduction catalyst, a gas outlet of each one of the reactors provided with the CO 2 storage-reduction catalyst is connected to a gas inlet of at least one different reactor provided with the CO 2 storage-reduction catalyst, other than the one reactor, via a purge gas recirculation line which supplies the purge gas containing CO 2 emitted from the gas outlet of the one reactor into the gas inlet of the different reactor, each one of the reactors provided with the CO 2 storage-reduction catalyst has a feature capable of alternately carrying out the storing of CO 2 and the reducing of CO 2, and at least one of the reactors provided with the CO 2 storage-reduction catalyst is configured for carrying out the storage of CO 2 and simultaneously a remaining reactor provided with the CO 2 storage-reduction catalyst is configured for carrying out the reducing of CO 2.