||The solubility of CO2 in three ionic liquids which contains two different number of cyanide anions, 1-butyl-3-methylimidazolium dicyanamide ([c4mim][N(CN)2]), 1-butyl-3-methylimidazolium tricyanomethanide ([c4mim][C(CN)3]) was measured. The solubility of CO2 was determined by measuring the bubble point pressure or cloud point pressure at the temperature ranges from 303.15 to 373.15 K in 10 K intervals. Also, the measured data were correlated with the PR-EoS incorporated with the conventional van der Waals one fluid mixing rule. The critical properties of ionic liquids were estimated using the modified Lydersen-Joback-Reid method. As a result, [c4mim][C(CN)3] has higher CO2 solubility than [c4mim][N(CN)2]. It implies that the CO2 solubility is affected by the number of cyanide anions contained in ionic liquid. From this result, it is concluded that the cyanide anion enhances the CO2 solubility in ionic liquid and that the ionic liquid which contains more cyanide anion has higher CO2 solubility.