PROBLEM TO BE SOLVED: To provide a substance that promotes formation of tight junction, or a substance which induces expression of tight junction protein 1, or a substance which induces cell membrane localization of the tight junction protein 1, and a medicine or the like containing the substance.SOLUTION: A tight junction formation promoter, a tight junction protein 1 expression-inducing agent, a tight junction protein 1 cell membrane localization inducer, and a medicine, drink and food, and a skin external preparation containing the substance which have phenylethylamine derivative or synephrine as an active ingredient.SELECTED DRAWING: None