The formation of indentation cracking has some relationship with the transformation stress induced by martensitic transformation, besides the relationship with the residual stress by volume change in the plastic zone in ZrO_2 laminated ceramics. Whereas surface residual compressive stress controls the expansion of surface cracks. Contributions of the transformation driving force and surface compressive stress are not considered in the traditional indentation theory. Therefore, fracture toughness value measured by the traditional method is usually lower than the practical one in ZrO_2 laminated ceramics. When indentation-fracture method is used, the value is more reliable.