Since plastic deformations occur in contact between silicon nitride sphere and plate, the elastic/plastic stress analysis is required to evaluate the residual strength of ceramics, surface of which is damaged due to the sphere indentation. For the purpose of evaluating elastic/plastic sphere indentation damages and residual strength of ceramics, an approximate analysis of elastic/plastic contact deformation in ceramics was carried out. The elastic/plastic internal stresses of the ceramic plate were also analysed by using the finite element method. Reasonable correlation between the maximum residual stress caused at surface in the tangential direction due to sphere indentation and the residual strength was obtained.