A control system comprising: an external device; and a control device for controlling machines or facilities, the control device comprising: first communication means configured to transmit and receive data in accordance with a first protocol, the first communication means including a first timer that defines a time of data transmission and is configured to be time-synchronized with an entity to and from which data is transmitted and received; second communication means configured to transmit and receive data in accordance with a second protocol different from the first protocol, the second communication means including a second timer that defines a time of data transmission and is configured to be time-synchronized with an entity to and from which data is transmitted and received; an interface for connection to the external device including a third timer; and synchronization means configured to time-synchronize the first timer and the second timer, wherein the synchronization means time-corrects the second timer with respect to the first timer, and wherein the synchronization means is configured to time-synchronize each entity time-synchronized with the second communication means with the second timer which has been time-corrected, characterized in that the synchronization means time-corrects the first timer and the second timer with respect to the third timer of the external device, and in that the synchronization means includes: means configured to set the third timer to output a synchronization signal to the first timer at a designated third time; means configured to read a fourth time in the first timer, which is stored when the synchronization signal output from the third timer is detected by the first timer, from the first timer; and means configured to instruct the first timer to correct time on the basis of a difference between the third time and the fourth time. an external device; and a control device for controlling machines or facilities, the control device comprising: first communication means configured to transmit and receive data in accordance with a first protocol, the first communication means including a first timer that defines a time of data transmission and is configured to be time-synchronized with an entity to and from which data is transmitted and received; second communication means configured to transmit and receive data in accordance with a second protocol different from the first protocol, the second communication means including a second timer that defines a time of data transmission and is configured to be time-synchronized with an entity to and from which data is transmitted and received; first communication means configured to transmit and receive data in accordance with a first protocol, the first communication means including a first timer that defines a time of data transmission and is configured to be time-synchronized with an entity to and from which data is transmitted and received; second communication means configured to transmit and receive data in accordance with a second protocol different from the first protocol, the second communication means including a second timer that defines a time of data transmission and is configured to be time-synchronized with an entity to and from which data is transmitted and received; an interface for connection to the external device including a third timer; and synchronization means configured to time-synchronize the first timer and the second timer, wherein the synchronization means time-corrects the second timer with respect to the first timer, and wherein the synchronization means is configured to time-synchronize each entity time-synchronized with the second communication means with the second timer which has been time-corrected, characterized in that the synchronization means time-corrects the first timer and the second timer with respect to the third timer of the external device, and synchronization means configured to time-synchronize the first timer and the second timer, wherein the synchronization means time-corrects the second timer with respect to the first timer, and wherein the synchronization means is configured to time-synchronize each entity time-synchronized with the second communication means with the second timer which has been time-corrected, characterized in that the synchronization means time-corrects the first timer and the second timer with respect to the third timer of the external device, and in that the synchronization means includes: means configured to set the third timer to output a synchronization signal to the first timer at a designated third time; means configured to read a fourth time in the first timer, which is stored when the synchronization signal output from the third timer is detected by the first timer, from the first timer; and means configured to instruct the first timer to correct time on the basis of a difference between the third time and the fourth time. means configured to set the third timer to output a synchronization signal to the first timer at a designated third time; means configured to read a fourth time in the first timer, which is stored when the synchronization signal output from the third timer is detected by the first timer, from the first timer; and means configured to instruct the first timer to correct time on the basis of a difference between the third time and the fourth time.