An image processing apparatus projecting 3D image data to 2D planar image data includes: an accumulation unit that accumulates the 3D image data having position coordinates and pixel values; an acquisition unit that acquires a display parameter, including a zoom parameter for changing image size, for the 2D image data to be created; a creation unit that creates the 2D image data from the 3D image data with the display parameter by determining a half view angle of the 3D image data and performing inverse projection transformation on the 2D image data while changing, in accordance with a change in the half view angle caused by the change in image size specified by the zoom parameter, an inverse projection transformation method applied to position coordinates used to create the 2D image data; and a display unit that displays the created 2D image data as a 2D planar image.