There is disclosed an embodiment for performing a calibration of a sensor by using an image registration between a three-dimensional ultrasound image and computerized tomography (CT) image. An ultrasound image forming unit includes an ultrasound probe and forms a three-dimensional ultrasound image of a target object. A sensor is coupled to the ultrasound probe. A memory stores a three-dimensional computed tomography (CT) image of the target object and position information on a position between the three-dimensional ultrasound image and the sensor. A processor performs image registration between the three-dimensional CT image and the three-dimensional ultrasound image to form a first transformation function for transforming a position of the sensor to a corresponding position on the three-dimensional CT image and performs calibration of the sensor by applying the position information to the first transformation function.