To provide a data monitor device capable of remote monitoring at a low cost, using the Internet.

Energy saving data are collected and stored at a remote station 4, and the accumulated data are fed to an Internet connecting device 5 at every fixed cycle and received by a monitor center 3 via the Internet 1. The remote station 4 is connected with the Internet connecting device 5 via a PLC(power line carrier) transmission line 6. In the monitor center 3, the energy saving data sent via the Internet 1 are received by an Internet connecting device 9, and the received data are displayed on monitor device 10.