Provided is a production method for a concentrated product, using a freeze-concentration method having a high yield rate (low loss rate) that is practically applicable, as required in large-scale (commercial scale) production. The production method for concentrated product using the freeze-concentration method comprises: an ice crystal generation step in which a fluid to be treated is cooled, ice crystals of the fluid to be treated are generated in the fluid to be treated, and a mixed fluid of ice crystals and concentrated fluid to be treated, being fluid to be treated that has been concentrated by the generation of the ice crystals, is formed； and an ice crystal separation step in which the mixed fluid is separated into the concentrated fluid to be treated and the ice crystals, and the concentrated fluid to be treated is retrieved.
