To provide a monitoring system of a doctor device capable of highly precisely determining the quality of a slide-contact state between a doctor blade and a plate cylinder based on quantified information on vibration.

The vibration of the doctor blade is detected by an acceleration sensor, and vibration information is extracted from a vibration signal based on a plurality of viewpoints. The tendency of chattering and fogging is detected from each extracted vibration information based on the plurality of viewpoints, and the presence of generation of chattering or fogging which requires warning is determined based on the detection result. Based on the result of detecting the tendency of chattering or fogging from each extracted vibration information based on the plurality of viewpoints, in order to cancel the tendency, correction of the angle of the doctor blade and correction of pressure applied to the doctor blade from an air cylinder 5 are performed.