We have carried out a long-term measurement of prestressing force in permanent ground anchor which were employed to buildings. On the measurement results, we confirmed the time change properties of prestressing force and analyzed the quantity of each decrease by three known factors, relaxation of pulling materials, creep of the anchor fixation ground and subsidence right under the foundation which was tense and fixed ground anchors. Furthermore, we inspected the prediction method that was assumed at the time of the design, of prestressing force which was held 60 years later.
