An experimental apparatus equipped with three density meters was newly developed for measuring vapor-liquid-liquid phase separation properties at high pressures. Coexisting phase composition and saturated density of each phase can be measured by means of the present apparatus with a maximum temperature of 400 K and pressure of 20 MPa, The phase compositions of carbon dioxide + ethanol mixture and their densities at high pressures were measured at 308.15 K with the apparatus. The sensitivity and absolute reliability of the equilibrium compositions appear to be 0.0001 and 0.001 mole fractions, respectively. The accuracy of saturated densities is 0.1 kg/m(3). The equilibrium compositions obtained in the present study were correlated with the pseudocubic equation of state previously proposed by the authors and the Soave-Redlich-Kwong equation of state. Saturated densities obtained in the present study were further evaluated by the equations of state with the interaction parameters determined from vapor-liquid equilibrium data.