To provide a method for the manufacture of polyphenols that enables industrial manufacture of polyphenols containing water-soluble proanthocyanidins from grape seeds. The seeds of grape berries dried after squeezing out the juice are separated into grape seeds and peel with a separation apparatus, and the grape seeds are stirred in a washing machine to remove contamination thoroughly. The grape seeds are charged into a boiling kettle and heated for the prescribed time at the prescribed temperature. Then, germination is induced in a curing kettle maintained at the prescribed temperature preferred for the germination. The grape seeds in which germination or germination and differentiation have advanced are crushed, mixed with water to obtain an emulsified state, and a salt is added, if desired. After a known desalting treatment has been conducted with respect to an aqueous solution portion, water is evaporated with a vacuum apparatus to obtain polyphenols comprising proanthocyanidins converted to a water soluble form.