PROBLEM TO BE SOLVED: To provide a technology for preventing erroneously detecting whether or not a radiation imaging device is irradiated with a radiation.SOLUTION: A radiation imaging device comprises: a pixel array 101 in which a plurality of pixels including a conversion element 201 for converting a radiation to an electric charge and a switch element T for connecting the conversion element with a signal line are arranged a bias line Vs for giving bias potential to conversion elements a plurality of drive lines G connected with control terminals of switch elements a drive unit 102 that supplies a drive signal for each drive line group and repeats initialization operation of switching the state of each drive signal from an off-voltage state, in which switch elements become non-conductive, to an on-voltage state, in which switch elements become conductive, before returning the state to the off-voltage state an acquisition unit that, a plurality of times, acquires signal values showing bias current in each drive period from the time of having switched the state of a drive signal for a drive line group to the on-voltage state to the time of switching the state of a drive signal for the next group to the on-voltage state a calculation unit 130 for calculating radiation information on the basis of the signal values and a determination unit 131 for determining the existence of irradiating the pixel array with a radiation, on the basis of the radiation information.SELECTED DRAWING: Figure 1
