To prevent the reaction force side of a deformation sample from inclining which is unavoidable, even in a highly rigid reaction force frame in a shear testing device for structures.

Three cylinders for exerting vertical forces and two cylinders for exerting shearing forces are used, instead of a highly rigid reaction force frame. Displacements are controlled, in reference to a stationary beam so as to maintain the target locations of the five cylinders in absolute coordinates, to prevent the reaction force fixed part of the sample from inclining.