PROBLEM TO BE SOLVED: To provide a technique which is advantageous to uniformize detection performance for detecting the irradiation of radiation.SOLUTION: A radiation imaging apparatus includes a pixel array where a plurality of pixels for capturing an image by the radiation are arranged, a detection part which outputs a detection value corresponding to the irradiation of the radiation, an adjustment part which adjusts the characteristics of the detection part, so that a relation between a signal outputted from the pixel array or a processing result obtained by processing the signal and the detection result comes to a predetermined relation, and a control part which detects that the radiation is irradiated, according to the fact that the detection value exceeds a threshold.SELECTED DRAWING: Figure 7
