Workpiece vibration is a crucial issue in machining of thin-walled workpieces because of their large compliance. The workpiece compliance should be considered in setting machining conditions to suppress the vibration. However, the conventional impact test is laborious, and its result depends on the operator’s skill. In this study, an on-machine measurement instrument was developed to measure the compliance of thin-walled workpieces. The developed measuring instrument can be attached to the machine tool spindle for automatic compliance measurement. The workpiece compliance measured by a swept sine excitation using the developed instrument was comparable to the compliance by the conventional impact test.