Each terminal devices (1, 4) connected to one another via a LAN (11) includes: a main control portion (e.g. 31) performing operational control, a transmission LAN unit (34) performing transmission control regarding transmission and reception of disaster prevention information. The unit (34) includes: a transmitting and receiving circuit (36) connected to the portion (31); a transmission control portion (35) performing communication control; an arrival order determining and retransmitting circuit portion (37) connected to the portion (35) and to at least three of transmitting and receiving ports (38) which are capable of connecting to the LAN. Upon receiving an incoming signal of disaster prevention information from one of the portion (35) and the ports (38), the portion (37) outputs the received signal to the rest of them while shutting out for a predetermined period of time an incoming signal from the rest of the ports (38) that has sent the signal.