A topical composition for treating or preventing acne vulgaris which comprises at least one saturated or unsaturated chain alcohol having 18 carbon atoms represented by formula (1): ##STR1## wherein a dotted line represents either the presence or the absence of a double bond as an active ingredient, makes it possible to inhibit proliferation of Propionibacterium acnes, which causes acne vulgaris, or kill the bacterium to effectively treat or prevent acne vulgaris. The compound represented by formula (1) can be easily synthesized and has an extremely low toxicity. Furthermore, it exerts an excellent antibacterial effect on Propionibacterium acnes even when used at a relatively low concentration. Thus it can be used only in a small amount , which ensures a high safety.