When a tunnel has no problem therein, a reception wave of a broadcast is retransmitted into the tunnel. At this moment, terminal registers prevent a retransmission signal from leaking from the tunnel and do not influence an adverse effect to a broadcast wave outside the tunnel. When an accident occurs in the tunnel, sensors sense this fact, and a monitoring center issues an emergency operation instruction to broadcast equipment for an emergency. At this moment, the broadcast equipment stops the retransmission of the reception wave to broadcast emergency alarm information into the tunnel and also controls transmitting antennas to emit broadcast signals to broadcast the alarm information also nearby tunnel mouths.