The invention enables a verifier to easily confirm that the image data was captured in the multiple exposure mode, and also to easily confirm which area in the image captured in the multiple exposure mode was greatly affected by multiple exposure. An image generating unit generates exposure image data pieces by exposing an image sensor a plurality of times. An image composition unit combines exposure image data pieces to generate a single piece of composite image data. A reference image generating unit generates reference image data composed of data pieces for distinguishing pixel positions at which the exposure amount exceeds a threshold from the other pixel positions. A verification data generating unit generates verification data for determining whether alteration has been made from the composite image data and the reference image data to output a single file.