Provided is an external preparation comprising a complex containing: any one of a prostaglandin derivative, a pharmaceutically acceptable salt thereof and a hydrate thereof; and cyclodextrin, the prostaglandin derivative being represented by the following formula (I): (where R represents a group represented by the formula: —(CH2)4—S—CH2—CO2H, —(CH2)4—S—CH2—CO2CH3, —(CH2)4—C≡C—CO2H, —CH2—S—(CH2)2—S—CH2—CO2H, or —CH2—S—(CH2)4—CO2H), so that storage stability and content uniformity of the compound of the formula (I) are ensured.