An apparatus and method for displaying, on a medical image, template data corresponding to an implant. The apparatus and method include a storing the template data and a predetermined portion distance of a predetermined portion of a representation by the template data, a displaying the stored template data, measuring length information of the displayed template data, specifying an error range of the variable magnification of the displayed template data, and judging, based on the measured length information and the stored predetermined portion distance, whether the variable magnification of the displayed template data is within the specified error range.
