An image processing device for generating and updating three-dimensional data representing a biological tissue based on tomographic data of the biological tissue acquired by a sensor that acquires the tomographic data while moving through a lumen of the biological tissue, and causing a display to display the three-dimensional data as a three-dimensional image includes: a control unit configured to color, in the three-dimensional image, at least a voxel representing an inner surface of the biological tissue or a voxel that is adjacent to the voxel representing the inner surface and that represents the lumen among a first voxel group corresponding to a cross section indicated by tomographic data newly acquired by the sensor, in a manner of being distinguished from a second voxel group corresponding to another cross section of the biological tissue.