A vertical type of double disc surface grinding machine of the present invention comprises a clamp device which can clamps and holds a work like a brake disc at a correct clamping position under a stable state even when a configuration of a work upper surface is complicated. The quick-connecting coupler has a first male-end and a second female end. Further, at least one embodiment is directed to a dual-source CT device in which the detectors have different widths in the system axis direction.