Provided is a state determination device for a structure and a state determination method for a structure, which are able to determine the state of the structure by a simple configuration. This state determination device (10) for a structure comprises a vibration detection means (11) for detecting the vibration of the structure, and an arithmetic means (12) for performing arithmetic processing on vibration waveform data acquired by the vibration detection means (11), and the arithmetic means (12) comprises an approximate curve acquisition means (121) for acquiring an approximate curve of the envelope of the vibration waveform data, and a determination means (122) for determining the state of the structure with reference to a threshold value provided in the difference between the approximate curve and the vibration waveform data.
