To obtain the subject agent having direct treating and improving effect on various kinds of arteriosclerosis and exhibiting excellent safety by using natural geranylgeraniol as an active component.

This agent contains geranylgeraniol of the formula as an active component. The compound of the formula is a natural substance available in the market and having high safety. The daily clinical administration rate of the compound of the formula for adult is usually 10-2,000mg, preferably 30-1,500mg. The present agent enables the direct and safe treatment and amelioration of arteriosclerosis in contrast with conventional indirect treating method.