Disclosed is a structure analyzing device and a structure analyzing method which can analyze a state change of a structure, which is caused before the structure is destroyed, such as a state change of degradation of the structure or the like. A structure analyzing device (10) includes a vibration detecting unit (11) which detects a vibration of a structure, and an analysis unit (12) which analyzes an output signal of the vibration detecting unit (11). The analysis unit (12) analyzes a state change of the structure by comparing a value of resonant sharpness Q, which is measured by use of the following formula (1) in a state existing when carrying out analysis, with a value of resonant sharpness Q which is measured by use of the following formula (1) in a standard state.