1. An endoscope image processing device comprising: an image acquisition section that acquires image signals that form a front image corresponding to a front field of view and a side image corresponding to a side field of view as a single acquired image; and a boundary region correction section that performs an overlapping process that causes at least one of an image of a front region and an image of a side region to overlap a boundary region that is a region that defines a boundary between the front region and the side region, the front region being a region within the acquired image that corresponds to the front field of view, and the side region being a region within the acquired image that corresponds to the side field of view, the boundary region being a region that corresponds to a specific angle of view based on an optical design value of an optical system for capturing the front field of view and the side field of view, a first boundary line that is a boundary line between the boundary region and the front region being set on an inner side relative to the region that corresponds to the specific angle of view, and a second boundary line that is a boundary line between the boundary region and the side region being set on an outer side relative to the region that corresponds to the specific angle of view.