1. An apparatus for enabling a biopsy needle to be observed in a three-dimensional ultrasound image comprising: means for transmitting ultrasound signals towards a target object and receiving echo signals reflected from the target object; means for forming a three-dimensional volume image by receiving and combining two-dimensional data from said transmitting means; means for extracting the target object from the three-dimensional volume image; means for estimating a location of the extracted target object and a location of the biopsy needle that is inserted into the extracted target object; means for displaying the extracted target object; and means for calculating an error in location between the biopsy needle and the extracted target object based on said estimation and providing the calculated error to said estimating means.