For the purpose of investigating the mechanics of folding process that is formed in relatively shallow underground, we have conducted buckling tests on single layer and threelayered rock beams of KIMACHI sandstone and TOHOKU marble under moderate confining pressures, namely 0, 100, 300 and 500 kg/cm².
From this study, it became clear that folding deformation of rock beam under moderate confining pressure initiates at the near point of buckling fracture stress, and failure strength of those conform to the buckling experimental formula suggested by Shanley. Also, by means of conducting buckling test using intact rock, we confirmed that folding degree of multilayered rock beam depends on thickness of unit beam rather than total thickness of beam, and that of multilayered beam constituted with various rocks depends on competent layer.