A radiation imaging apparatus having a battery and being operable in at least one of a plurality of power supply forms including the battery and an external power source, the apparatus comprising: a power control unit configured to determine the power supply form; and a control unit configured to control an operation of the radiation imaging apparatus, wherein in accordance with the power supply form, the control unit switches between a first obtaining mode of obtaining offset correction data after imaging of an object for each imaging of the object and a second obtaining mode of obtaining offset correction data obtained in advance before imaging of an object is done, and the control unit switches to the first obtaining mode if power is supplied from the battery and switches to the second obtaining mode if power is supplied from the external power source.