Machine tools that are capable of large-scale complex processing are in high demand. However, the drum-type ATC, currently being used, has difficulty in maintaining rigidity due to the increased weight of the tool. Thus, a ring-type ATC that would provide rigidity while reducing costs is considered. The tool replacement shaft of the cam box, one of the main components of ATC, is greatly affected by the increase in tool weight and load acting in various directions. Thus, its fatigue life should be considered. A life test can be conducted to determine its fatigue life, but because the required life is long, the test takes a considerable amount of time. This problem can be solved by using the accelerated life test, but the parameter data required to perform the test are insufficient. In this study, we present a structural analysis of the cambox shaft, derive the shape parameters required for an accelerated life test, and confirm that the parameters derived using data bagging techniques are accurate.