A mill blank for dental CAD/CAM for preparing a dental restoration by being installed in a CAD/CAM device, wherein, the mill blank for dental CAD/CAM has a columnar shape, has at least two recesses which includes a first recess opening to an upper surface of the mill blank and a second recess opening to a bottom surface of the mill blank and at least one notched portion in a circumference portion, the first recess and the second recess respectively include a first surface which is parallel to the upper surface and the bottom surface and a second surface which is a circumferential face concentric with the circumferential face of the mill blank and is vertical to the first surface, and the notched portion is composed of a surface parallel to the center axis of the columnar shape of the mill blank and contacts with the second surface.