A noise monitoring device capable of easily estimating a noise generation source in a factory is connected for communication with a plurality of machines in the factory. The noise monitoring device is provided with a noise information acquisition unit configured to acquire noise information including the time of generation of noise if the noise is generated in the machines, an operation information acquisition unit configured to continually acquire operation information of all the machines, a determination unit configured to extract the operation information at a point in time near the noise generation time, and a display unit configured to display the noise information and the operation information of all the machines at the point in time near the noise generation time.