An image processing device includes: a determination unit that determines, based on a plurality of pieces of image data which is generated by continuously taking images of an area of field of view and input from an imaging unit provided outside the image processing device, whether the area of field of view of the imaging unit has been changed; an image composition unit that superimposes overlapping areas of imaging regions of a plurality of images corresponding to the plurality of pieces of image data along a direction in which the area of field of view of the imaging unit has been changed, to generate composite image data when the area of field of view of the imaging unit has been changed; and a display control unit that causes a display unit provided outside the imaging processing device to display a composite image corresponding to the generated composite image data.