To obtain an activated oxygen scavenging agent capable of sufficiently scavenging the activated oxygen generated in the living body and having a high safety.

This activated oxygen scavenging agent contains a pectin or its hydrolysate, especially an oligo galactulonic acid expressed by the formula [(n) is 0 or a natural number] and having 1-100, preferably 1-5 degree of polymerization, or its salt as an active ingredient. This agent can be used to prepare the composition of a cosmetic material, a medicine, a food, a beverage, etc. In the cosmetic material, by scavenging the activated oxygen, it is effective for preventing a wrinkle formation, a depilation, the generation of a body smell, etc., and contains 0.01-10wt.% composition. In the medicine, by preparing the preparations with the optional components by using the usual method and it is orally administered in 10-100mg/adult/day by dividing it one to several times, or administered in 5-500mg by an injection. In the food, 0.01-10wt.% agent is blended and prepared to a confectionery such as a candy, a jerry, etc., a beverage, and a bread. This agent is effective for the treatment of inflammation, senile dementia, myocardial infarct, allergic diseases, hepatic disturbances, rheumatoid arthritis, etc.