A control system of an excavating machine controls the excavating machine including a work machine, and includes a communication unit communicating with an outside of the excavating machine and receiving construction information related to an object to be excavated that is excavated by the work machine, a storage unit storing the construction information received by the communication unit, a work machine control unit executing excavation control to control an operation of the work machine not to erode the object to be excavated based on position of the work machine and the construction information stored, and a processing unit determining whether updating construction information to be used by the work machine control unit for the excavation control to the new construction information received by the communication unit according to a control state of the work machine by the work machine control unit.