The present invention was accomplished for the purpose of developing a method for effectively treating and/or preventing synucleinopathies, and is based on a discovery that an adiponectin receptor agonist suppresses α (alpha)-synuclein aggregation, tau phosphorylation and a decrease in proteasomal activity.The method of the present invention for treating and/or preventing neurodegenerative diseases includes a step of administering an effective dose of at least one effective element selected from a group consisting of: adiponectin as an adiponectin receptor agonist; a compound inducing expression of adiponectin; globular adiponectin; and a compound inducing expression of globular adiponectin. The present invention further provides a screening method of the adiponectin receptor agonist for treating and/or preventing neurodegenerative diseases.