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, wherein the boundary region is an annular 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, and wherein the boundary region correction section includes a boundary line setting section that sets a first boundary line that is a boundary line between the boundary region and the front region and that is set on an inner side relative to the annular 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 and that is set on an outer side relative to the annular region that corresponds to the specific angle of view.