A medical image diagnosis device according to an embodiment includes: a mask image generation unit that generates a plurality of mask images that are different in terms of time; a first image generation unit that calculates differences between a plurality of the mask images, and extracts an image of a preceding device that is placed and kept in a blood vessel; a second image generation unit that generates a real-time fluoroscopic image depicting a situation where an insertion device is being inserted into a blood vessel, calculates a difference between the real-time fluoroscopic image and the mask image, and generates an image of the insertion device; an image synthesis unit that synthesizes images generated by the first image generation unit and the second image generation unit; and a display unit that displays an image generated by the image synthesis unit.