To provide a method for producing β-chitin and chitosan hydrate which are useful as a functional food having excellent digestibility and absorptivity, by using cuttlebone as a raw material and processing it through a high- pressure megapascal method and an acid hydrate treatment, and to provide a method for utilizing the same for food.

This method for producing the β-chitin and chitosan hydrate comprises utilizing crude β-chitin and chitosan which are decalcified and deprotenized. Further, acid hydrate of the β-chitin and chitosan, a sol-type product thereof, and an aqueous solution-type product thereof are obtained by the method. The products thus prepared are utilized for food or the like.