An ultrasound diagnostic apparatus includes a light source information setting unit setting light source data indicating a property of a light source irradiated to a cross section region of the object, an optical property setting unit setting a weight coefficient indicating an optical property of cross-section region data including intensity information on the cross section region to the light source, an illuminance slice data creation unit calculating illuminance at positions corresponding to coordinates of a plurality of the cross-section regions based on the light source data and the weight coefficient, and creating illuminance slice data of the plurality of the cross-section regions based on the calculated illuminance, and a composition unit compositing a two-dimensional cross-section image of the object from the plurality of illuminance slice data.