Even when the radiation image detector comprises a rechargeable internal power supply means, and to charge the internal power supply means and by supplying power from an external power source, and preventing the signal of the photographed image data or the like is affected by noise to provide a radiation image detector of the possible. An external power supply terminal 27 for supplying the battery 28 power to each part, and rechargeable battery 28 by receiving the power supplied from the external power source PW, the received power from the external power source PW via the external power supply terminal 27 and a cassette controller 30 for controlling the supply to the battery 28, when it detects an external power supply terminal 27 has to receive power from an external power source PW, and determines the operating status of each functional unit, the cassette controller 30, the the and controls the supply to the battery 28 of the received power from the external power source PW via the external power supply terminal 27 according to the operating state of the functional unit.充電可能な内部給電手段を備える放射線画像検出器において、外部電源から電力を供給して内部給電手段の充電を行う場合にも、実写画像データ等の信号がノイズの影響を受けるのを防止することのできる放射線画像検出器を提供する。各部に電力を供給するバッテリ28と、外部電源PWから供給される電力を受電してバッテリ28を充電可能とする外部給電端子27と、外部給電端子27を介して外部電源PWから受電した電力のバッテリ28に対する供給を制御するカセッテ制御部30を備え、カセッテ制御部30は、外部給電端子27が外部電源PWから電力を受電したと検知したとき、各機能部の稼動状態を判断し、この各機能部の稼動状態に応じて外部給電端子27を介して外部電源PWから受電した電力のバッテリ28に対する供給を制御する。
