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 said fluid are generated in said fluid, and a mixed fluid to be treated is formed wherein said mixed fluid to be treated is comprised of said ice crystals and a concentrated fluid produced from said fluid to be treated by generating said ice crystals in said fluid thereby said fluid is concentrated； and an ice crystal separation step in which said mixed fluid is separated into said concentrated fluid to be treated and said ice crystals, and said separated concentrated fluid be treated is retrieved.
