A filament current that is to be supplied to a filament of an x-ray tube under imaging conditions, from the imaging conditions of the tube current and the tube voltage that is to be supplied to the x-ray tube at the time of radiographic imaging, are stored as a filament current setting value in a storing portion, and the difference between an anticipated value for the tube current when x-ray emission is performed at a given filament current and a measured value for the tube current when x-ray emission is actually performed at that filament current is measured over time as a tube current value difference, and when the mean value for the tube current value difference over a specific time interval exceeds a setting value that has been set in advance, the filament current setting value that is stored in the storing portion is corrected.