1. A medical-data processing device for processing three-dimensional space data outputted from a tomographic apparatus, the medical-data processing device comprising: a body-surface identifying device configured to identify a body surface region by performing contour extraction process to the three-dimensional space data, the body surface region corresponding to a body surface of a stereoscopic image of a subject; an intensity adjusting device configured to adjust intensity of the body surface region in the three-dimensional space data; and an image generating device configured to generate a maximum-intensity projection image in accordance with the three-dimensional space data having the intensity adjusted, wherein the intensity adjusting device decreases the intensity of the body surface region, whereby the image generating device generates the image by selecting the maximum intensity from a portion of the three-dimensional space data except for the body surface region.