Provided is a method for removing CO2 comprising: supplying a gas to be processed containing CO2, N2 and O2 to a feed side of a CO2/O2 selective permeation membrane within a temperature range of 15° C. to 50° C.; generating water vapor and supplying the water vapor to the CO2/O2 selective permeation membrane; selectively removing CO2 from the gas to be processed by permeating CO2 in the gas to be processed from the feed side to a permeate side of the CO2 selective permeation membrane selectively to O2 and N2 in the gas to be processed; and using a CO2 facilitated transport membrane having CO2/O2 selectivity and CO2/N2 selectivity within the temperature range as the CO2 selective permeation membrane, the CO2 facilitated transport membrane being configured with a hydrophilic polymer containing an amino acid and a deprotonating agent for preventing protonation of an amino group of the amino acid supported by a porous membrane, wherein a CO2 concentration in the gas to be processed is 3 mol % or less on a dry basis.