PURPOSE: To produce vinegar free from stimulating odor which vinegar has, retaining stable quality without causing separation of the ingredients when allowed to stand for long period and retaining the initial rich nutrients which sea grasses have.

CONSTITUTION: A sea grass such as sea tangle, wakame sea grass and edible brown algae is dried and pulverized and sugar solution is added thereto to saccharify the sea grass. Then saccharifying enzyme and yeast are added to the resultant saccharified solution and the saccharified solution is subjected to alcohol fermentation to provide an unrefined vinegar. Then ethanol is added to the resultant unrefined vinegar to control the unrefined vinegar to definite the alcoholic concentration and further a seed vinegar is added thereto and the unrefined vinegar is subjected to acetic acid fermentation at about 32-37°C for 4-5 month and when the acidity of the fermented liquid is raised to about 4.5%, the fermented liquid is moved to a storage tank and allowed to stand for 5-6 month.