A method including carrying out adiabatic cooling and evaporation operation of a coolant in a crystallizer (20) for a mixture solution of a target organic compound containing the coolant; taking out crystal slurry produced by the operation from the crystallizer (20); pressurizing evaporated vapor to a pressure higher than the operation pressure in the crystallizer (20) by a compressor (30) and then introducing the vapor to an absorption condenser (10); cooling for condensation the mixture solution of organic compound and the evaporated vapor that has been pressurized while allowing them to contact each other in the absorption condenser (10); introducing the crystal slurry taken out of the crystallizer (20) to a purification means (70) for purification of the crystal; and introducing a clarified liquid in the purification means (70) to at least one of the crystallizer (20) and the absorption condenser (10).