A housing of an electronic cassette has an inclined surface which is formed between a side surface and a rear surface thereof and inclined relative to the side surface and the rear surface. An antenna opening through which a radio wave is transmitted is formed on the inclined surface. Since the antenna opening is formed on the inclined surface, the antenna opening is not blocked by a rear plate of a holder of an upright radiographic stand or a supine radiographic stand, and the antenna opening is not blocked by a side panel of an outer grid. Both in the case where the electronic cassette is set to the holder and in the case where the outer grid is attached to the electronic cassette, it is possible to perform stable wireless communication.
