To provide a control system in which optional information transmission can be performed between a line information terminal device provided in the vicinity of a production line and an information terminal device connected to the line information terminal device through a communication network.

A line indicator (line information terminal device) 3, a web server 6, a PC (information terminal device) 7 are connected through the communication network 4, and the web server 6 is provided with a folder for communication for storing data that are transmitted between the line indicator 3 and the PC 7. The web server 6 prepares data of a web image to be displayed on the opposite displaying parts 3a and 7a of the line indicator 3 and the PC 7 on the basis of data written in the folder for communication from either the line indicator 3 or the PC 7.