Use with a first absorbing liquid (A1, A1') and a second absorbing liquid (A2, A2') comprising respectively an amine absorbent of the same species in different concentrations, wherein the amine absorbent is selected from alkanolamines, and hindered amines having an alcoholic hydroxyl group, of a carbon dioxide recovery apparatus , comprising: an absorption column configured to bring a gas (G) into contact with an absorbing liquid (A1, A2) and to allow the absorbing liquid to absorb carbon dioxide contained in the gas, the absorption column having a first absorbing section and a second absorbing section which are arranged to supply the gas through the first absorbing section into the second absorbing section; a regeneration column that regenerate the absorbing liquid, configured to heat the absorbing liquid (A1', A2') having carbon dioxide absorbed in the absorption column to cause the absorbing liquid to release the carbon dioxide (C), the regeneration column having a first regenerating section having an external heating implement and a second regenerating section arranged to be heated by heat from gas discharged from the first regenerating section; and a circulation system having a first circulating path configured to circulate the absorbing liquid between the first absorbing section and the second regenerating section, and a second circulating path configured to circulate the absorbing liquid between the second absorbing section and the first regenerating section, wherein the absorbing liquid circulated in the first circulating path is the first absorbing liquid (A1, A1') and the absorbing liquid circulated in the second circulating path is the second absorbing liquid (A2, A2'), and the concentration of the amine absorbent in the first absorbing liquid is higher than that in the second absorbing liquid. an absorption column configured to bring a gas (G) into contact with an absorbing liquid (A1, A2) and to allow the absorbing liquid to absorb carbon dioxide contained in the gas, the absorption column having a first absorbing section and a second absorbing section which are arranged to supply the gas through the first absorbing section into the second absorbing section; a regeneration column that regenerate the absorbing liquid, configured to heat the absorbing liquid (A1', A2') having carbon dioxide absorbed in the absorption column to cause the absorbing liquid to release the carbon dioxide (C), the regeneration column having a first regenerating section having an external heating implement and a second regenerating section arranged to be heated by heat from gas discharged from the first regenerating section; and a circulation system having a first circulating path configured to circulate the absorbing liquid between the first absorbing section and the second regenerating section, and a second circulating path configured to circulate the absorbing liquid between the second absorbing section and the first regenerating section, wherein the absorbing liquid circulated in the first circulating path is the first absorbing liquid (A1, A1') and the absorbing liquid circulated in the second circulating path is the second absorbing liquid (A2, A2'), and the concentration of the amine absorbent in the first absorbing liquid is higher than that in the second absorbing liquid. <EOS>