It is intended to provide an anti-inflammatory agent made from a highly safe material which can be daily taken as a food, an agent for preventing or ameliorating allergic diseases and a functional food having the above-mentioned effects. The anti-inflammatory agent contains an .alpha.-bond galactooligosaccharide as the active ingredient. The agent for preventing or ameliorating allergic diseases contains an .alpha.-bond galactooligosaccharide as the active ingredient. The functional food contains an .alpha.-bond galactooligosaccharide as the active ingredient. As such .alpha.-bond galactooligosaccharide, use can be made of a product synthesized by the dehydration condensation reaction by .alpha.-galactosidase with the use of galactose or galactose-containing substance as a substrate.