To provide a radiographic image detecting device that has improved graininess of a radiographic image since electric power supplied from a power source includes power supply noise in a radiographic image detecting device using a TFT read system and then noise is included even in a readout signal output from a scan driving circuit to a TFT switch element and flows out as a noise signal to a signal line to be added to electric charge read out by a readout circuit, so that graininess of a radiographic image is made worse.

A switch SW1 is prepared between a TFT switch element and a predetermined OFF voltage source 302 which supplies a predetermined OFF voltage to the TFT switch element, and is turned off while a signal converter 671 performs at least CDS so that the noise generated at the OFF voltage source 302 is blocked.