A structural health monitoring system that is configured to monitor structural health of a structural object having a plate-like first inspection area and a second inspection area, the first inspection area having no bent portion, the second inspection area including a bent plate-like portion, the structural health monitoring system comprising: - an ultrasonic transducer that is configured to oscillate an ultrasonic wave to the first inspection area; - an ultrasonic sensor that is configured to detect a waveform of at least one of a transmission wave of the ultrasonic wave and a reflected wave of the ultrasonic wave, the transmission wave having been transmitted through the first inspection area, the reflected wave having been reflected in the first inspection area; - a strain sensor that is configured to detect a strain amount of the second inspection area and that is attached to the second inspection area including the bent plate-like portion; and - a signal processing part that is configured to obtain at least one index, representing health of the structural object including the first inspection area and the second inspection area, based on the waveform detected by the ultrasonic sensor and the strain amount detected by the strain sensor, wherein the signal processing part is configured to determine whether there is a possibility that a defect has arisen in the first inspection area, based on the detected strain amount in the second inspection area, wherein the signal processing part is configured to segment the second inspection area into areas, and to determine whether there is the possibility that a defect has arisen in the first inspection area, based on the strain amount in a selected area out of the segmented areas, the selected area being closest to the first inspection area, and wherein the system further comprises: - a control circuit that is configured to control the ultrasonic transducer to oscillate the ultrasonic wave toward the first inspection area when the signal processing part has determined that there is the possibility that a defect has arisen in the first inspection area. the first inspection area having no bent portion, the second inspection area including a bent plate-like portion, the structural health monitoring system comprising: - an ultrasonic transducer that is configured to oscillate an ultrasonic wave to the first inspection area; - an ultrasonic sensor that is configured to detect a waveform of at least one of a transmission wave of the ultrasonic wave and a reflected wave of the ultrasonic wave, the transmission wave having been transmitted through the first inspection area, the reflected wave having been reflected in the first inspection area; - a strain sensor that is configured to detect a strain amount of the second inspection area and that is attached to the second inspection area including the bent plate-like portion; and - a signal processing part that is configured to obtain at least one index, representing health of the structural object including the first inspection area and the second inspection area, based on the waveform detected by the ultrasonic sensor and the strain amount detected by the strain sensor, - an ultrasonic transducer that is configured to oscillate an ultrasonic wave to the first inspection area; - an ultrasonic sensor that is configured to detect a waveform of at least one of a transmission wave of the ultrasonic wave and a reflected wave of the ultrasonic wave, the transmission wave having been transmitted through the first inspection area, the reflected wave having been reflected in the first inspection area; - a strain sensor that is configured to detect a strain amount of the second inspection area and that is attached to the second inspection area including the bent plate-like portion; and - a signal processing part that is configured to obtain at least one index, representing health of the structural object including the first inspection area and the second inspection area, based on the waveform detected by the ultrasonic sensor and the strain amount detected by the strain sensor, wherein the signal processing part is configured to determine whether there is a possibility that a defect has arisen in the first inspection area, based on the detected strain amount in the second inspection area, wherein the signal processing part is configured to segment the second inspection area into areas, and to determine whether there is the possibility that a defect has arisen in the first inspection area, based on the strain amount in a selected area out of the segmented areas, the selected area being closest to the first inspection area, and wherein the system further comprises: - a control circuit that is configured to control the ultrasonic transducer to oscillate the ultrasonic wave toward the first inspection area when the signal processing part has determined that there is the possibility that a defect has arisen in the first inspection area. - a control circuit that is configured to control the ultrasonic transducer to oscillate the ultrasonic wave toward the first inspection area when the signal processing part has determined that there is the possibility that a defect has arisen in the first inspection area.