Provided is a device for detecting a malfunction of a rotating machine, the device being able to early detect the malfunction and to have a reduced size. The device includes a detecting unit (1) for detecting vibration of the machine, sampling a signal indicative of the vibration with a predetermined sampling frequency, and outputting, at a time at intervals of a predetermined period, a plurality of the sampled data detected within the predetermined period, a storage (21) and an HDD (22) for storing the plurality of the sampled data, a frequency analyzer (23a) for analyzing the frequency of the plurality of the sampled data, a determination unit (24) for performing a primary determination based on the result of the analysis, a display unit (3) for displaying the result of the analysis in chronological order and in real time, and a communication unit (6) for transmitting the plurality of the sampled data to an information-processing device for performing a secondary determination.