To provide a clamp device that can grip a plurality of loads reliably irrespective of their rigidity, and is simple is structure and relatively inexpensive to manufacture.

An arm portion 24 of each clamp arm 16 has a holding portion 30 recessed in a clamp surface 16a, and a curved wall surface 32 defined within the holding portion 30 to support a movable grip member 20 movably. The movable grip member 20 has first grip surfaces 34a extending linearly along the arm portion 24 in projected related to the clamp surface 16a of the arm portion 24, and a support surface spreading on the counter side to the first grip surfaces 34a which is covered with the holding portion 30 and extending arcuately along the arm portion 24 and concavely to the first grip surfaces 34a. The support surface has the substantially same curvature as the curved wall surface 32 of the arm portion 24 so as to come into uniform sliding contact with it. In the contact state, the movable grip member 20 is movable back and forth along the arm portion 24 about the center axis of the curved wall surface 32.