To provide an earthquake-proof diagnostic system that can easily acquire the earthquake-proof performance of a building.

An earthquake-proof diagnostic system vibrates a building by installing a horizontal movement vibration generator 20 on the second floor of the building, detects acceleration of the vibration by the generator with vibration detectors (21, 22 and 23), and includes an analyzer 15 performing analysis processing predetermined by receiving detection signals from at least two of the vibration detectors (21, 22 and 23). The analyzer performs an analysis concerning acceleration values and frequencies of vibration for respective detection signals to detect the frequency of the vibration as a dynamic natural frequency fm (HZ) of the building when the acceleration value shows a peak value and calculates a dynamic wall area index Md of the building by using the detected dynamic natural frequency fm and a predetermined natural frequency 4.98 (Hz) in an earthquake-proof grade I and using a predetermined expression Md=(fm/4.98)2. The analyzer further calculates dynamic scores Hd for at least respective walls of the building and calculates a dynamic wall area index Md' of the building by using Md'=(fm/5.57)2.