Abstract: A rotor includes a high-temperature section and a low-temperature section on its circumference. It is possible to absorb and separate carbon dioxide gas in an effluent or exhaust gas simply by rotating the rotor. Therefore, it is possible to obtain a reliable absorbing/separating system. The system can be remarkably simplified, the regenerating cost thereof can be considerably reduced, and the maintenance thereof is easy. A fixed type of system has similar advantages. Lithium zirconate, an alkali metal oxide, and/or an alkali earth metal oxide is used as an absorbing/separating agent. Such an absorbing/separating agent is chemically and mechanically stable, and can absorb and release carbon dioxide gas stably and reversibly.