PURPOSE: To easily concentrate brewed vinegar in high efficiency, by neutralizing a brewed vinegar with an alkaline substance to form a brewed vinegar salt, concentrating the salt solution, adding an excess acidic substance to isolate acetic acid and subjecting it to distillation under reduced pressure.

CONSTITUTION: A brewed vinegar such as rice vinegar is neutralized with an alkaline substance (e.g. sodium hydroxide). The obtained solution of brewed vinegar salt is concentrated under heating and added with an excess acidic substance (e.g. hydrochloric acid) to isolate acetic acid. The product is distilled under reduced pressure (e.g. at 35W55°C under 20W50mmHg vacuum) to obtain a concentrated vinegar.