1. An X-ray diagnostic imaging method for radiographing a predetermined area of a subject so as to acquire image data of contrast image including a figure of a contrast medium flowing in an affected part, and for displaying and retaining the image data of the contrast image, comprising the steps of: radiographing the predetermined area so that an image data of a first contrast image is acquired when a timing of an acquired start of the first contrast image comes, after an injection of the contrast medium into the affected part; and radiographing the predetermined area so that an image data of a second contrast image is acquired when a timing of an acquired start of the second contrast image comes, after the image data of the first contrast image is acquired.