The structural materials which are used in high temperature components have various shapes. Thus, the site of stress concentration might have the heterogeneous microstructural distribution, which resulted in the occurrence of unpredictable fracture. Therefore, it is necessary to clarify the relationship between the heterogeneous microstructural distribution around notch tips and creep fracture mechanism for these materials in order to predict the life of creep fracture with a high degree of accuracy to maintain operational safety and minimize operational costs. In this study, the creep crack growth tests were performed using in-situ observational testing machine with microscope to observe the creep damage formulation and creep crack growth behavior. The materials used are polycrystalline Ni-base superalloy IN100 and directionally solidified Ni-base superalloy CM247LC which were developed for the jet engine turbine blade and the gas turbine blade for electric power plants, respectively. The specimen used is a Double Edge Notched (DEN) specimen. After the tests, the microstructural observation of the test specimens was conducted using FE-SEM/EBSD. Additionally, the analyses of two-dimensional elastic-plastic creep finite element using designed methods to find out the creep damage region were conducted to understand the effect of microstructural distribution on creep damage formulation. As a result, the experimental and analytical results showed that it is important to determine the creep crack initiation and early crack growth to predict the life of creep fracture and it is indicated that the high accurate prediction of creep fracture life could be realized by measuring notch opening displacement proposed as the RNOD characteristic.