<p>A clamp device has a clamp arm reciprocatably installed on an installation member, pressing force applying means for applying pressing force to the clamp arm, and a clamp bolt for clamping a material to be clamped between the bolt and a support member. A threaded tube having an external thread portion on its outer side and an internal thread portion on its inner side is installed on the clamp arm such that its height position is adjustable using the external thread portion. A clamp bolt is screwed in the internal thread portion of the threaded tube. There is provided an operation portion for performing swing operation of the clamp bolt with the material to be clamped being clamped between the clamp bolt and the support member.</p>
