A carbon dioxide separation membrane according to the present invention includes: an ionic liquid affinitive porous layer (C) having an ionic liquid-containing liquid (A) retained in voids; and an ionic liquid non-affinitive porous layer (B). The ionic liquid affinitive porous layer (C) may contain inorganic materials (for example, metal oxide particles having an average particle size of about 0.001 to 5 μm on a number basis). An average thickness of the ionic liquid affinitive porous layer (C) may be about from 0.01 to 10 μm. The ionic liquid affinitive porous layer (C) may include the ionic liquid-containing liquid (A) at a ratio from 0.1 to 99 parts by volume with respect to 100 parts by volume of voids. It may be a carbon dioxide separation membrane for fertilizing plants with carbon dioxide. The carbon dioxide separation membrane can reduce a size of the carbon dioxide concentrating device and enables smooth operation of the device.