1. A portable radiographic imaging apparatus comprising: an image output unit which detects a radiation which penetrates an object to be imaged and is irradiated on a surface to be irradiated of a casing, and outputs data of a radiographic image which represents a distribution of an amount of irradiated radiation; a first storage unit which stores the data of the radiographic image output from the image output unit; a display unit which displays an image; and a display control unit which allows the display unit to display a previously captured radiographic image which is associated with a current imaging, before the object to be imaged is imaged.