According to the present embodiment, an image diagnosis apparatus includes a first image taking device that takes an image of a patient placed on a couchtop by using an X-ray emission; a second image taking device that takes images in positions by moving an image taking position of the patient by a predetermined distance at a time, along the body-axis direction; a position estimating unit; and a correction processing unit. The position estimating unit estimates a couchtop position for each of the image taking positions of the second image taking device, based on information about warping of the couchtop of the first image taking device. The correction processing unit uses information about the couchtop positions estimated by the position estimating unit, for performing a position correcting process on the images obtained by the image taking devices.