1. A medical image diagnosis apparatus comprising: a controller that generates a plurality of candidates for a first cross-sectional image from three-dimensional image data obtained by taking images of a heart, generates, from the three-dimensional image data, one or more second cross-sectional images each of which intersects the candidates for the first cross-sectional image, and displays in parallel on a display, the candidates for the first cross-sectional image, as well as the second cross-sectional images on each of which information is superimposed, wherein the information indicating positional relationships between the candidates for the first cross-sectional image and the second cross-sectional image.