An image processing device for causing a display to display, as a three-dimensional image, three-dimensional data representing a biological tissue includes: a control unit configured to form, in the three-dimensional data, a cutting region exposing a lumen of the biological tissue in the three-dimensional image, and cause the display to display, together with the three-dimensional image, a two-dimensional image representing a cross section of the biological tissue and a region corresponding to the cutting region in the cross section.