PURPOSE: To produce grain vinegar having high nutritive value, slight acetic acid smell, aroma, and a soft feeling in drinking, by blending grain with Chlorella or spirulina, brewing the blend.

CONSTITUTION: Grain (e.g., raw or treated unpolished rice or adlay, etc.) is blended with Chlorella or spirulina (may be cultivated in the open air or indoor, and cultivated and may be directly used or dried and used), a starchy material in the blend is saccharified with a koji, and protein contained in the blend is decomposed into amino acids with a protease of the koji. In the process, an extract component, vitamin, mineral, etc. in Chlorella, etc. are also transferred to a saccharide solution part. Then, the blend is subjected to alcohol fermentation, and subjected to acetic acid fermentation by stationary culture method. The prepared grain vinegar has a large amount of nutrient components resulting from grain, Chlorella, etc., has slight acetic acid smell, aroma and a soft feeling in drinking, and is excellent as edible vinegar.