Sacrificial specimen is a small sized fatigue specimen which is designed so that fatigue damage may be produced in the specimen sufficiently earlier than in a structural member when it is secured to the structural member. In the previous study, a sacrificial specimen which is secured onto the structural member by using adhesive agent is developed. And the fatigue property of the sacrificial specimen was investigated under constant stress amplitude. In this study, the sacrificial specimen is adhered to a smooth specimen or a welded joint specimen and the fatigue test is carried out under block loading with exponential distribution. It is found that the sacrificial specimen shows a stable fatigue property under block loading and has a high sensitivity for fatigue damage. Fatigue crack is produced in the sacrificial specimen sufficiently earlier than in the welded joint. Further, a method to predict fatigue life of structural member is developed based on the fatigue damage condition monitored in the sacrificial specimen.