A communication system includes a destination base station that performs wireless communication with a terminal and is a communication destination; a neighboring base station; and a relay station that relays the wireless communication between the terminal and the destination base station. The relay station notifies the destination base station of information on the neighboring base station capable of communicating wirelessly with the relay station, as neighboring base station information, wherein when wireless communication between the destination base station and the relay station is disconnected, the destination base station makes an inquiry to the neighboring base station with reference to the neighboring base station information, and wherein the destination base station determines that abnormality has occurred in the relay station when wireless communication between the relay station and the neighboring base station is not confirmed.