This image processing device is capable of displaying three-dimensional data representing a body tissue as a three-dimensional image on a display, and is provided with a control unit which performs control so as to form, in the three-dimensional data, a cutting area through which an inner cavity of the body tissue is to be exposed in the three-dimensional image and to cause a two-dimensional image representing a portion corresponding to the cutting area in one cross-sectional plane of the body tissue to be displayed at a position corresponding to said one cross-sectional plane in the three-dimensional image.