Provided is a prevention or treatment agent for cerebral amyloid ² beta storage diseases, that contains a substance capable of suppressing the progression, alleviating the symptoms, and improving cerebral amyloid beta storage diseases. This prevention or treatment agent for cerebral amyloid beta storage diseases has as an effective component thereof a compound (e.g., Iguratimod) indicated by formula (1) or a salt thereof and, as a result, is capable of preventing or treating cerebral amyloid beta storage diseases such as Alzheimer-type dementia or cerebral amyloid angiopathy.
