The disclosure is related to a device and method for obtaining a complete and accurate three-dimensional surface image of a target object by registering a three-dimensional optical image with a volume data obtained by X-ray imaging. The device for generating a three-dimensional surface image for dentistry includes a three-dimensional imaging module including an optical camera which obtains a three-dimensional optical image of the target object and an X-ray imaging unit which obtains X-ray images of the target object in multiple directions, a reconstruction unit generating a volume data by reconstructing the X-ray images, and an image processing unit registering the three-dimensional optical image with the volume data and generating a three-dimensional surface image of the target object by substituting a different portion of the three-dimensional optical image with a boundary of the volume data.
