To provide a system for normally and continuously monitoring the situation of an apparatus to be monitored such as a reefer container, and performing intensive management.

The system includes: signal converters 3 to be connected to the serial interfaces of respective operation control parts 2 in a plurality of models of reefer containers 1; a connection processor 4 to which one or a plurality of signal converters 3 are connected, and which individually identify the operation state of each reefer container 1, based on the output signal; a data collecting server 100 for performing transmission/reception via one or a plurality of connection processors 4, a container side radio LAN device 5, and a monitor side radio LAN device 101; and a monitoring personal computer 102. Each signal converter 3 performs mutual conversion between a short distance transmission signal with the operation control parts 2 and a long distance transmission signal with the connection processors 4. Each connection processor 4 selects a different communication method by the model of each reefer container 1, fetches monitor data from the signal converters 3, converts the monitor data into the one in a prescribed form, and transmits the resultant data.