PURPOSE: To obtain a fermentation raw material containing flavor of seaweeds and mineral component, by treating seaweeds with cellulase enzyme to convert polysaccharides in seaweeds into fermentable saccharide.

CONSTITUTION: Seaweeds are treated with cellulase enzyme, polysaccharides contained in the seaweeds are converted into fermentable saccharides by hydrolyzing β-1,4 glucoside of polysaccharides with cellulase, a cellulose hydrolyzing enzyme. Consequently, a seaweed material comprising a fermentable raw material to undergo alcohol fermentation is obtained. The seaweed material is subjected to alcohol fermentation or alcohol fermentation and acetic acid fermentation and optionally further distilled so that various mineral components in the seaweeds are eluted and liquor or vinegar sufficiently provided with flavor components can be obtained. Endo-1,4-β-glucanase, exo-1,4-β-glucanase, β-D- glucosidase, etc. may be cited as the cellulase used.