To provide a system for monitoring the stagnation status of component plate materials put in a stand-by status without starting working after the component plate materials enter the work area of a process.

A component identification tag 1 is arranged for each type of component plate material m. The component identification tag 1 is provided with a radio ID tag and a display part, and the identification information of the type of the component plate material is stored therein, and optional information to be viewed by a person is displayed. The entrances of work areas 12 and 13 of at least one process are provided with process entrance section detection means 23 and 25 for detecting the stored information of the radio ID tag of the component identification tag 1. Mechanical section detection means 24 and 26 are respectively arranged in each plate material working machines 15 and 16. The quantity of component plate material m put in a stand-by status in work areas 12 and 13 is monitored by an in-process stagnation monitoring means 35 from the detection information of the process entrance section detection means 23 and 25 and the mechanical section detection means 24 and 26.