A control system comprising: a field bus to which slave devices are linearly connected through a communication cable ; a first controller which is connected to one end of the field bus; a second controller which is connected to the other end of the field bus; and an information communication network that connects the first controller and the second controller without going through the slave devices, wherein each of the first controller and the second controller includes a control frame generation part which generates a control frame to be provided to the slave devices, and a transception part which transmits and receives the control frame to and from the slave devices , and one of the first controller and the second controller generates the control frame by the control frame generation part, transmits the generated control frame from the transception part , and the other one performs loopback communication of the control frame by the transception part through the communication cable and the slave devices , when the first controller generates and transmits the control frame and the second controller performs the loopback communication of the control frame, the second controller transmits an operation confirmation signal to the first controller through the information communication network , and starts generation and transmission of the control frame when a response signal to the operation confirmation signal is not able to be received, wherein the first controller in a run mode exclusively executes cyclic control of the slave devices (21, 22, and 23), and the second controller in a data acquisition mode exclusively executes storage of the control frame for abnormality detection and transmission of the control frame to the information communication network . a field bus to which slave devices are linearly connected through a communication cable ; a first controller which is connected to one end of the field bus; a second controller which is connected to the other end of the field bus; and an information communication network that connects the first controller and the second controller without going through the slave devices, wherein each of the first controller and the second controller includes a control frame generation part which generates a control frame to be provided to the slave devices, and a transception part which transmits and receives the control frame to and from the slave devices , and one of the first controller and the second controller generates the control frame by the control frame generation part, transmits the generated control frame from the transception part , and the other one performs loopback communication of the control frame by the transception part through the communication cable and the slave devices , when the first controller generates and transmits the control frame and the second controller performs the loopback communication of the control frame, the second controller transmits an operation confirmation signal to the first controller through the information communication network , and starts generation and transmission of the control frame when a response signal to the operation confirmation signal is not able to be received, wherein the first controller in a run mode exclusively executes cyclic control of the slave devices (21, 22, and 23), and the second controller in a data acquisition mode exclusively executes storage of the control frame for abnormality detection and transmission of the control frame to the information communication network . <EOS>