A housing of an electronic cassette includes an inclined surface. The inclined is formed between a side surface and a rear surface of the housing and inclined relative to the side surface and the rear surface. The inclined surface is provided with indicators for displaying a center position of each side of an imaging area and operation conditions of the electronic cassette. Each of the indicators consists of a light source and a display window through which light from the light source is emitted to the outside. The display window is formed on the inclined surface. Since the display window is formed on the inclined surface, the display window is not blocked by an outer grid.