This paper describes a method for quantitatively evaluating the falling of concrete pieces from tunnel linings, comparing the shear stress acting on crack surfaces with the shear capacity. The shear capacity of cracks of various width, inclination angle and roughness were investigated by double shear tests simulating the fall of concrete pieces and on a simulation method, whose applicability is also described in this paper. The resisting capacity against the fall of concrete pieces was estimated using the proposed method under conditions reproducing an actual tunnel.