A control system, comprising: 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, an A system communication control unit including a data combining unit and a collation unit (125, 126), and a B system communication control unit including a data combining unit and a collation unit (145, 146), wherein the A system arithmetic unit with the A system communication control unit and the B system arithmetic unit with the B system communication control unit have a duplex configuration, the A system arithmetic unit and the B system arithmetic unit are separated by a gap such that wirings between the units do not cross, 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, wherein a frame which is transmitted to the A system communication control unit and the B system communication control unit from the A system arithmetic unit is transmitted by being divided, a frame which is transmitted to the A system communication control unit and the B system communication control unit from the B system arithmetic unit is transmitted by being divided, a response frame which is transmitted to the A system arithmetic unit from the A system communication control unit is collectively transmitted without being divided, a response frame which is transmitted to the B arithmetic unit from the B system communication control unit is collectively transmitted without being divided, and the response frames from the A system communication control unit and the B system communication control unit are not collated in the arithmetic device. 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, an A system communication control unit including a data combining unit and a collation unit (125, 126), and a B system communication control unit including a data combining unit and a collation unit (145, 146), wherein the A system arithmetic unit with the A system communication control unit and the B system arithmetic unit with the B system communication control unit have a duplex configuration, the A system arithmetic unit and the B system arithmetic unit are separated by a gap such that wirings between the units do not cross, 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, wherein a frame which is transmitted to the A system communication control unit and the B system communication control unit from the A system arithmetic unit is transmitted by being divided, a frame which is transmitted to the A system communication control unit and the B system communication control unit from the B system arithmetic unit is transmitted by being divided, a response frame which is transmitted to the A system arithmetic unit from the A system communication control unit is collectively transmitted without being divided, a response frame which is transmitted to the B arithmetic unit from the B system communication control unit is collectively transmitted without being divided, and the response frames from the A system communication control unit and the B system communication control unit are not collated in the arithmetic device.