To provide a new system for efficiently adsorbing and separating carbon dioxide, one of substances causing global warming effect, and finally efficiently reducing discharge amount of carbon dioxide without unintentionally discharging desorbed carbon dioxide to the outside of the system.

The adsorbing system of carbon dioxide is provided in which an adsorbent composed of powder having aluminum oxide as a principal component is filled into a cylindrical or rectangular parallepiped adsorption vessel having a gas supply port and a gas discharge port; carbon dioxide-containing gas is introduced to the gas supply port; carbon dioxide is selectively adsorbed in the adsorbent in the adsorption vessel; and gas with reduced concentration of carbon dioxide is discharged from the gas discharge port.