There is provided an acidic gas absorbing agent that is large in absorption amount and high in absorption rate of an acidic gas per unit volume and can prevent the diffusion of ingredients of the absorbing agent. The acidic gas absorbing agent includes an amino acid salt of formula 1 or formula 2 and an amine compound of formula 3. wherein COOMe represents a carboxylate group; Me represents an alkali metal. R1 and R2 represent an C1-4 alkylene chain ; R3 represents a cycloalkyl group; R4 represents a hydrogen atom or an C1-4 alkyl group; and R5 represents a hydroxyalkyl group. The total number of carbon of alkyl chains of the R1 and the R2 is more than 1 and less than 5.