To provide a highly reliabile remote monitoring device with which images, sounds, control data and monitor data or the like can be transmitted/ received through a radio transmission line and interruption caused by a transmission/reception error is reduced.

This device is provided with an image receiver 10 having an input/output part 14 for data, a control part 12 for data and a radio communication part 16 and plural image transmitters 20 respectively having a radio communication part 22, control part 24 and input/output part 26, and the image receiver 10 successively scans and detects the presence/absence of data transmission requests from the respective image transmitters 20. Concerning the image transmitter 20 which requests transmission, the radio transmission line is opened, and compression encoded image data are transmitted from that image transmitter 20 to the image receiver 10.