PURPOSE: To obtain viscous vinegar having improved flavor and taste, by carrying out continuous two-stage fermentation by the use of acetic acid bacteria belonging to the genus Acetobacter or Gluconobacter.

CONSTITUTION: Viscous vinegar is obtained by using the following continuous fermentation processes of (a) and (b). (a) The fermentation process wherein a belonging to the genus Acetobacter or Gluconobacter, capable of producing a viscous substance, is cultivated to produce the viscous substance. (b) The fermentation process wherein the culture mixture prepared by the fermentation process a is incorporated with a nutrient source necessary for acetic acid fermentation and acetic acid fermentation is carried out by acetic acid bacteria belonging to the genus Acetobacter or Gluconbacter. Any substance produced by acetic acid bacteria belonging to the genus Acetobacter or Gluconbacter can be used as the viscous substance. Acetobacter polysaccharogens MT-11-2(FERM BP-112) can be used as the acetic acid bacteria.