PURPOSE: To improve the efficiency of communication by means of a controller by selecting communication lines whose communication method connecting plural controllers to each other are different from each other and a using communication line corresponding to the monitoring result of a communication situation of each line of this.

CONSTITUTION: Communication is executed mutually between controllers (PC) A to G, between a robot 21 and a sensor 22, and respectively between with a network (NW) monitor 1 through the communication lines 50 to 54 of different communication system. When a communication request is generated, one of PCs retrieves a communication device table, selects a communication route by which communication is possible with a communication opposite side and obtaines the fault and idle information from the monitor 1. Based on this information PC selects each communication route of different communication speed from a result obtained by calculating the communication time of each communication route and the priority of communication request and the working situation, etc., of the line. Thereby communication efficiency is improved between PCs and between PC, the robot and the sensor.