A radiation detector includes radiation detection elements for detecting radiations which have penetrated an object as electric signals, with the elements arranged in a two-dimensional array, and an image display controller for producing a radiation image of the object detected as the electric signals with the radiation detector as continuous images including a plurality of frames. The image display controller switches a tube voltage of a radiation source for emitting the radiations between a first voltage at a time of producing odd images and a second voltage at a time of producing even images and controls a display device to continuously display a plurality of processed images as a dynamic image. Each of the processed images are obtained by performing a subtraction process between an odd image of the odd images and an even image of the even images, wherein the even image is derived in succession to the odd image.