There is provided user equipment of a radio communication system that supports D2D communication, the user equipment including a receiver configured to receive a predetermined synchronization signal; a synchronization processor configured to perform a process for synchronizing with the predetermined synchronization signal; and a transmitter configured to transmit a synchronization signal in a subframe that is the same as that of a synchronization signal transmitted from any other user equipment when the synchronization signal transmitted from the other user equipment is received by the receiver and received power of the synchronization signal transmitted from the other user equipment is less than a predetermined threshold value, wherein the transmitter interrupts transmission of the synchronization signal for a predetermined time interval, and the receiver measures the received power of the synchronization signal transmitted from the other user equipment in the predetermined time interval.