An electronic cassette is provided with a sensor panel, a housing, operation buttons, a head-bottom setting section, lamps and a memory. The sensor panel has a quadrangle imaging area, and detects an X-ray image of a patient. The housing houses the sensor panel. The operation buttons are disposed on the housing. When either one of the operation buttons is pushed down, the head-bottom setting section sets either one of adjoining two sides of the imaging area to be the head of the radiographic image in the display orientation. The display section is disposed on the housing, and displays which side is set by the head-bottom setting section to be the head of the radiographic image. The memory stores head-bottom setting information and the radiographic image in association with each other.