The present invention addresses the problem of providing an agent and a method for suppressing the progression of tauopathy such as Alzheimer-type dementia. 1-(3-(2-(1-benzothiophen-5-yl)ethoxy)propyl)azetidin-3-ol or a salt thereof has an effect of decreasing the level of phosphorylated tau protein and on decreasing the level of amyloid-ß protein in the brain parenchyma, and is useful as a prophylactic or therapeutic agent for tauopathy. Thus, it is possible to prevent or treat tauopathy by administering 1-(3-(2-(1-benzothiophen-5-yl)ethoxy)propyl)azetidin-3-ol or a salt thereof.
