An object of the present invention is to provide a novel and excellent agent for treating or preventing dementia, schizophrenia, and the like, based on the serotonin 5-HT 5A receptor modulating action. It was confirmed that a bicyclic acylguanidine derivative which has a characteristic structure that guanidine is bonded to one ring of a bicyclic structure such as chromene and dihydronaphthalene through a carbonyl group and a cyclic group is bonded on the other ring, has a potent 5-HT 5A receptor modulating action and an excellent pharmacological action based on this mechanism. The present invention is useful as an excellent agent for treating or preventing dementia, schizophrenia, bipolar disorder, or attention deficit hyperactivity disorder.
