Fracture toughness (KIC) values were measured on the major planes of single-crystal silicon using the controlled surface flaw (CSF) and indentation fracture (IF) methods at room temperature. The values of KIC on the surface orientations {100}, {110}, {111} and {112} obtained by the CSF method were found to be 1.13, 1.12-1.14, 1.18 and 1.11-1.18MPa·m0.5, respectively. It was found that these KIC values increased slightly with increasing the Young's modulus perpendicular to the fracture surfaces. Though KIC values obtained by the IF method, on the other hand, were scattered significantly (0.82-1.18MPa·m0.5), its Young's modulus dependence was similar to that obtained by CSF method.