Phase behavior of the water in CO₂ microemulsion that nano size water droplets were dispersed into CO₂ were investigated, and considered the effect of the organic solvents on the phase behavior of this. In order to form the microemulsion, sodium salt of bis(2,2,3,3,4,4,5,5-octafluoro-1-pentanol) sulfosuccinate(F-AOT) surfactant which has CO₂ philic chains and hydrophilic head group simultaneously was synthesized. The added ten organic solvents were iso-propanol, n-propanol, ethanol, methanol (group 1), tetrahydrofuran, pyridine, 2-methoxyethanol (group 2), acetonitrile, acetone, 1,4-dioxane (group 3). These organic solvents were added into water+surfactant+CO₂ and the cloud points of this microemulsion were measured. In case that the organic solvents of group 1 were added into water+surfactant+CO₂ microemulsion, the cloud points were 22.15-28.70 MPa (T = 317.1-363.20 K) for methanol, 18.5-28.40 MPa (T = 307.5-357.20 K) for ethanol, 17.40-28.32 MPa (T = 307.20-365.30 K) for n-propanol, 15.15-26.49 MPa (T = 309.15-365.60 K) for iso-propanol. In case of the organic solvent of group 2, the cloud points were 19.3-28.2 MPa (T = 308.15-367 K) for acetone, 18.8-26.3 MPa (T = 307-356.1 K) for 2-methoxyethanol, 18.6-27.9 MPa (T = 309.1-368.2 K) for tetrahydrofuran, 16.2- 25.9 MPa (T = 307.1-367.5 K) for pyridine. In case of the organic solvent of group 3, the cloud points were 16.52-26.74 MPa (T = 307-359.3 K) for acetonitrile, 19.3-28.2 MPa (T = 308.15-367.0 K) for acetone, and 20.1-28.8 MPa (T = 309.15-364.15 K) for 1,4-dioxane. According to the results, the cloud point of water+surfactant+organic solvent+CO₂ becomes lower in adding the ten orgarnic solvents, and the phase behavior of this microemulsion was related to the solubility parameter of organic solvent and CO₂.