A control system includes an arithmetic device configured of an A system arithmetic unit including a data dividing unit, a B system arithmetic unit including a data dividing unit, and an A system communication control unit including a data combining unit and a collation unit, wherein the A system arithmetic unit and the B system arithmetic unit have a duplex configuration, the A system arithmetic unit and the B system arithmetic unit are separated by a gap, a frame output from the A system arithmetic unit is transmitted to a B system communication control unit through the A system communication control unit and an interface element, and a frame output from the B system arithmetic unit is transmitted to the A system communication control unit through the B system communication control unit and an interface element.