1. An image registration device, comprising: a feature extractor configured to extract, from a first medical image, a first feature group and to extract, from a second medical image, a second feature group; a feature converter configured to convert, using a converted neural network in which a correlation between features is learned, the extracted second feature group to correspond to the extracted first feature group, to obtain a converted group; and a register configured to register the first medical image and the second medical image based on the converted group and the extracted first feature group.