A control system includes a control device. The control device has a first communication unit and a second communication unit respectively connected to distinct networks distinct from each other, and a timer that manages a time-indicative value. The control device collects first communication data transmitted and/or received by the first communication unit, associates the collected first communication data with a value indicating a time point at which this communication data is transmitted and/or received, and stores the resulting first communication data. The control device collects second communication data transmitted and/or received by the second communication unit, associates the collected second communication data with a value indicating a time point at which this communication data is transmitted and/or received, and stores the resulting second communication data.