To provide a method for freeze-concentrating an aqueous solution, wherein the apparatus cost and the operating cost are low, and the operation is simple.

This method comprises repeating a series of the steps of: cooling the feed solution in the tower to the melting point of the objective liquid concentrate or lower to deposit ice crystals; heating the inside of the tower in a heat- insulated state from its top to allow the molten ice crystals to downwardly flow through the tower; withdrawing the concentrated fraction having an average concentration equal to the concentration of the objective liquid concentrate from the bottom of the tower; withdrawing the middle fraction having an average concentration equal to the concentration of the feed solution from the bottom of the tower and blending it with the feed solution of the next operation; and discharging the residual ice crystals from the tower.