A diagnostic imaging apparatus includes a ventricular volume-variation measuring unit that measures sequential variations in a size of a ventricle within at least one heart beat, from images of a heart scanned in each of a plurality of time phases; a scanning-condition setting unit that specifies a time phase of little cardiac motion based on variations in the size of the ventricle measured by the ventricular volume-variation measuring unit, and sets scanning conditions so as to collect data in the specified time phase; and an imaging unit that collects data based on the scanning conditions set by the scanning-condition setting unit, and reconstructs an image from the collected data.