To achieve rational maintenance for fossil power plants, prediction of remaining life for structure components is quite important. Precise evaluation of critical flaw sizes, which provides failure criteria of the components with postulated crack-like-flaws under a specific operating condition, is one of the key issues. In this paper, fracture criteria of a structure material with a wide range of temperature including transition temperature range were examined. Based on the fracture test results, it is ascertained that fracture load can be well predicted by R6 procedure for assumed temperature range of interest.