Provided is a mobile communication system capable of eliminating the use of a control channel for transmitting specific area information and suppressing the overhead caused by a frequency change process for a mobile station to receive the specific area information. In the mobile communication system, a relay station (20) has a coverage area (21) (specific area) and relays and transmits, in the coverage area (21), a signal received from a base station (10) to a mobile station (30). The relay station (20) adds, to the signal received from the base station (10), the offset of any of a frequency offset, a time offset, and a power offset depending on a risk indicated by risk information in the coverage area (21) (specific area) and transmits the signal after the addition of the offset to the mobile station (30) located in the coverage area (21).