A method for efficiently resolving optical isomers, in which a discriminating liquid consisting of a discriminating agent capable of discriminating optical isomers and a diluent are brought into contact with a mixture containing said optical isomers in countercurrent flow, to resolve the optical isomers by adsorption separation, distillation separation, absorption separation or membrane separation, and recovered at an optical isomer content of 5 wt % or less for recycled use, under one or more of the following conditions: (a) the dielectric constant of the diluent is 30 or less and the viscosity of the discriminating liquid is 0.2 Pa·s or less at the temperature of the resolving operation; (b) the discriminating agent contained has the effect of splitting the 1H or 13C-NMR spectrum peak of the optical isomers when added and the diluent contained has a dielectric constant equal to or lower than the dielectric constant of the measuring solvent at the time of measuring the 1H or 13C-NMR spectrum; (c) the boiling point of at least one compound of the discriminating agent at the pressure of the resolving operation is higher than the boiling point of at least one compound of the diluent at the pressure of the resolving operation; (d) the boiling point of at least one compound of the diluent at the pressure of the resolving operation is higher than the boiling point of the optical isomers to be resolved, at the pressure of the resolving operation, by 10° C. or more; and (e) the concentration of the discriminating agent in the discriminating liquid is 10 wt % or more.