PROBLEM TO BE SOLVED: To provide an image processing system, device, method and a medical image diagnostic device for enabling an observer to perform various types of operations on a stereoscopic image by sensory operation.SOLUTION: An image processing system according to an embodiment includes a stereoscopic display device, a determining unit, and a rendering processing unit. The stereoscopic display device displays a stereoscopic image that is capable of being viewed stereoscopically using parallax images generated from volume data as three-dimensional medical image data. The determining unit identifies positional variation of a predetermined moving substance in a stereoscopic image space as a space in which the stereoscopic image is displayed by the stereoscopic display device from positional variation of the moving substance in a real space in which a coordinate system of the stereoscopic image space is present, and determines an operation content on the stereoscopic image on the basis of the identified positional variation. The rendering processing unit performs rendering processing on the volume data in accordance with the operation content determined by the determining unit to generate parallax images newly.
