A mobile communication system which supports D2D communication that is direct inter-terminal radio communication, comprises: a user terminal that transmits and receives discovery signals for a discovery process of a communication target terminal of the D2D communication; and a base station that transmits discovery resource information indicating radio resources to be used for transmitting and receiving the discovery signals. The user terminal transmits and receives the discovery signals when the discovery resource information is received from the base station, by using the radio resource indicated by the received discovery resource information.