Bias lines are provided for respective columns of pixels, and of a plurality of bias lines, bias lines provided at an interval of 10 mm are connected to a bias power source through a current detector. The remaining bias lines are connected directly to the bias power source without passing through the current detector. In each pixel, if electric charge is generated by a radiation detection element in accordance with the dose of irradiated radiation, a current flows in the bias line in accordance with the generated electric charge. The current detector detects the current flowing in the bias line, and a control unit detects, as the timing of starting irradiation of a radiation, when the detected current (current value) is equal to or greater than a threshold value, and starts radiographing of a radiological image.
