To obtain fundamental data for the extraction and concentration of furfural produced in a reactor by using supercritical CO₂, the isothermal high pressure vapor–liquid equilibria for two binary systems (CO₂–water and CO₂–furfural) and a ternary system (CO₂–water–furfural) were measured in the temperature range from 343 to 421 K. Additionally, the experimental data were compared with results calculated by various equations of state. As a result, it was found that (1) the Peng–Robinson and Soave–Redlich–Kwong equations of state combined with the mixing rules proposed by Panagiotopoulos correlated the two binary systems satisfactorily and predicted the ternary system well, and (2) the furfural produced could be selectively extracted from the reactor and concentrated to 95 wt% by a new process proposed on the basis of a knowledge of the vapor–liquid equilibria.