An object of the present invention is to provide a drug and a method which suppress progress of tauopathy such as Alzheimer's disease. 1-(3-(2-(1-Benzothiophen-5-yl)ethoxy)propyl)azetidin-3-ol or a salt thereof has an effect of reducing the amount of phosphorylated tau protein and an effect of reducing the amount of amyloid β protein in the brain parenchyma, and thus is effective as an agent for preventing or treating tauopathy. Tauopathy can be prevented or treated by administering 1-(3-(2-(1-benzothiophen-5-yl)ethoxy)propyl)azetidin-3-ol or a salt thereof.
