In order to improve the efficiency and reliability of fluid machinery, such as gas turbines and pumps, the control and suppression of secondary flow and separation inside fluid machinery is important. Fluid machinery faces a challenge in reducing losses caused by the flow through gaps at the tip of rotor blades. However, probe measurement in a narrow gap disturbs the flow field, so the measurement is difficult. Therefore, Mitsubishi Heavy Industries, Ltd. (MHI) has developed a thin flow angle measurement sensor in collaboration with the Tokyo University of Science, which can be applied to very narrow gaps while minimizing interference with the flow. The sensor was applied to an axial-flow compressor test machine to verify if it can measure flow angles. This report describes the outline of the developed thin flow angle measurement sensor and the axial flow compressor test results.