A system for detecting an abnormality of rotating machines includes two or more devices for detecting an abnormality and a computer. The respective devices include a sensor for detecting vibration of the respective rotating machines and generating signals indicative of the vibration, and a transmitting unit for transmitting the signals to the computer. The computer includes a sampler for sampling the signals with a sampling frequency and outputting, at a time at intervals of a predetermined period, a plurality of the data detected and sampled within the predetermined period, a storage for storing the data, a frequency analyzer for analyzing the frequencies of the data, a determination unit for determining whether the machines have an abnormality based on the results of the frequency analysis, and a display unit for displaying, in chronological order and in real time, the results of the frequency analysis and displaying the results of the determination.