A finished vinegar having an acetic acid concentration higher than 20 percent weight by volume is produced by repeating a fermentation cycle wherein a broth is fermented at 27.degree.-32.degree. C. in a 1st submerged fermentation tank by a continuous batch process, and, when the acetic acid concentration of the fermenting broth reaches 12-15 percent weight by volume, the large part of the fermenting broth in the 1st fermentation tank is withdrawn and charged in a 2nd submerged fermentation tank. The 1st fermentation tank is recharged with a mash and the fermentation of the fermenting broth in the 2nd tank is continued under aeration while lowering the temperature of the fermenting broth in such manner that the final fermentation temperature does not fall below 18.degree. C. and the lowering temperature does not become higher than the temperature once lowered.