Fracture toughness tests are carried out using three kinds of precracked specimen: (1) a specimen with a fatigue precrack introduced at an elevated temperature in a method proposed by the authors. (2) a specimen with a brittle precrack introduced by the bridge compression (BC) method proposed by Sadahiro et al., and (3) a specimen with a surface precrack introduced by Vickers hardness indentation. Fracture toughness evaluations by the chevron notch method and the indentation fracture method are also carried out. The precracks introduced by the three methods can not be assumed to be ideal cracks under the as-precracked condition. However, if the relevant treatments are made, the precracks are presumed to be ideal cracks, and almost the same fracture toughness values are obtained by using treated precracks. Based on these results, the authors recommend the method of precracking by cyclic fatigue at room temperature at the low ΔKfmax where a precrack introduced by the BC method is used as the starter for fatigue cracking.