To provide a structure deterioration diagnosis method also for coping with deterioration of a structure caused by its local corrosion/thickness diminution, and allowing simple, constructive, and quantitative evaluation to be made even without information on the structure in its construction or in its soundness.

This method includes a step for applying an impact force to the structure to measure a time waveform of vibration intensity of the structure caused by the applied impact, a step for finding the characteristic frequency of the structure from the measured time waveform of the vibration intensity, a step for finding the level of a stress put on the structure from the found characteristic frequency, a step for applying a periodical force to the structure to measure a temperature change of the structure caused by a thermoelastic effect owing to the applied force, a step for finding distribution of a stress put on the structure from the measured temperature change, a step for calculating maximum stress put on the structure from the found stress level and stress distribution, and a step for diagnosing the deterioration degree of the structure from the calculated maximum stress.