To obtain the subject adjuvant useful for promotion for growth of crops, greening of crops and prolongation of the term, improvement for resistance against diseases of crops, and increase of fruition and decrease of falling in fruit trees by formulating a vinegar obtained from chicory as an active ingredient.

The objective adjuvant is obtained by formulating a vinegar, which is obtained from chicory and includes fructooligosaccharide-containing saccharides containing inulin and fructooligosaccharide in an amount of 20 wt.% or more in the solid, as an active ingredient. The above vinegar is obtained by reacting a saccharide solution obtained by pressing the juice out from chicory with Saccharomyces ellipoideus yeast to allow to carry out alcohol fermentation and then allowing to carry out acetic acid fermentation by adding an acetic acid-fermented solution of the seed vinegar Acetobacter aceti. On this adjuvant, the concentration of fructooligosaccharide-containing saccharides and the acetic acid-converted acidity are adjusted to 2 wt.% or less and 0.5 wt.% or less, respectively, by diluting with water to be used.