A rendering method for generating relation information of image data of three or more dimensions. The rendering method includes preparing an exfoliated picture generated by projecting voxels using cylindrical projection method with a center line, preparing position data of a cross-section and a cross-section image representing the cross-section of the image data, creating a hypothetical cylinder including position data using the center line, calculating relation information associating the hypothetical cylinder and the cross-section using position data of the hypothetical cylinder and position data of the cross-section, and synthesizing the relation information with at least one of the exfoliated picture and the cross-section image to generate a synthesized image.