To provide a device and its system for detecting a radiation image, where its battery is quickly charged to secure a sufficient electric current capacity without the need to increase the diameter of an electric supply cable, or impose any increased burden on connectors, etc. used.

This is a cassette-type radiation image detector 2 having a battery 28 built in its casing 21 to supply the device functional parts with electric power, and driven by the electric power supplied from the battery 28. The device has a plurality of the detector-side connectors 26 structured to be electrically connected with a cradle 4 and/or a power supply cable 5 and receiving electricity from outside. The battery 28 is charged by receiving electricity from two or more detector-side connectors 26 in the charge of the battery 28.