An object is to provide a monitoring system capable of preventing the occurrence of a defect in paper by monitoring the device. The present invention is directed to a monitoring system A having a papermaking machine 1 for manufacturing paper X, an applying device 2 for applying a chemical solution to a site of the papermaking machine directly or indirectly in contact with the paper while the papermaking machine 1 is operated, a control panel 3 for setting an application condition of the applying device 2, a monitoring camera 4 for monitoring a monitoring target site, and a control device 5 connected to the monitoring camera 4 via a network. The monitoring target site is the site of the papermaking machine 1 directly or indirectly in contact with the paper X and/or the applying device 2, and the control device 5 has a computing unit S1 which converts a state of the monitoring target site into a numerical form by using video taken by the monitoring camera 4, a display unit S2 which displays detection data obtained by conversion into the numerical form at the computing unit S1, and a storage unit S3 which stores the detection data.