In order to improve the continuity of the image qualities in the minor-axis direction of plural sets of elastic frame data that constitute elastic volume data and generate a high-quality 3-dimensional elastic image, regarding each elastic frame data constituting elastic volume data, a noise frame interpolation unit subjects plural sets of elastic frame data including said elastic frame data and adjacent in a swing direction to synthesis processing, generates the elastic volume data from the synthesized plural sets of elastic frame data, and volume renders the elastic volume data to generate a 3-dimensional elastic image. The noise frame interpolation unit stores plural sets of elastic volume data, subjects plural sets of elastic frame data at corresponding swing angle positions among the stored plural sets of elastic volume data to synthesis processing to generate synthetic elastic frame data and elastic volume data from the synthesized plural sets of elastic frame data.