1. A method for producing a three-dimensional (3D) moving image of a moving target object, comprising the steps of: a) transmitting ultrasound signals to the moving target object and receiving reflected ultrasound signals; b) obtaining raw data based on the reflected ultrasound signals; c) generating image frame data including a plurality of image frames based on the obtained raw data; d) generating virtual image frame data including a multiplicity of virtual image frames, which are to be inserted between the plurality of image frames, based on the image frame data; and e) rendering a 3D moving image of the moving target object using the image frame and virtual image frame data.