To provide a radiation imaging apparatus which is capable of both connecting state radiographing for radiographing with a C arm connected and non-connecting state radiographing for radiographing with the C arm disconnected, and is convenient and obtains high quality images, the apparatus includes: a flat panel detector; a holding unit for holding at least the flat panel detector; and a control unit for controlling the flat panel detector. With the configuration, the flat panel detector can be connected to and disconnected from the holding unit; connecting state radiographing can be performed with the flat panel detector connected to the holding unit, and non-connecting state radiographing can be performed with the flat panel detector disconnected from the holding unit; the control unit controls the flat panel detector such that a heat generation quantity of the flat panel detector during the non-connecting state radiographing can be lower than a heat generation quantity of the flat panel detector during the connecting state radiographing.