A medical imaging diagnosis apparatus for measuring the composite thickness of the tunica intima and the tunica media of a blood vessel of a subject by acquiring image data on the blood vessel. In order to improve the accuracy of the IMT measurement of the composite thickness, the medical imaging diagnosis apparatus has extracting means for extracting the tunica intima and the tunica externa of the blood vessel on the basis of the brightness information of the image data to measure the composite thickness of the tunica intima and the tunica externa of the vessel in reference to the two extracted regions.