A servo system, comprising: a safety driver, configured to be connected to a drive device and comprising: a drive signal generation circuit configured to generate a drive signal driving the drive device based on an action command from a standard programmable logic controller, PLC, via a communication line and a feedback signal from the drive device, a drive signal path configured to transmit the drive signal from the drive signal generation circuit to the drive device, and a safety stop circuit configured to cut off the drive signal path when a stop instruction signal is input; and a safety controller, configured to be directly connected with the safety driver by a control signal line, to generate a first stop instruction signal in response to an input of an operator using an input part, and to output the first stop instruction signal to the safety stop circuit of the safety driver, wherein the safety driver comprises a first external device monitoring, EDM, output part configured to detect a cutoff of the drive signal path by the safety stop circuit and to output a first EDM signal to the safety controller indicating that the drive signal path is cut off, the servo system being characterized by further comprising a safety communication unit, configured to be connected with the safety driver and the safety controller, to generate a second stop instruction signal in response to an instruction from a safety PLC via the communication line, and to output the second stop instruction signal to the safety stop circuit of the safety driver, wherein the safety communication unit comprises a second EDM output part configured to output a second EDM signal to the safety controller in a case where the safety stop circuit is activated according to the first stop instruction signal output from the safety controller, and not to output the second EDM signal to the safety controller in a case where the safety stop circuit is activated according to the second stop instruction signal. a safety driver, configured to be connected to a drive device and comprising: a drive signal generation circuit configured to generate a drive signal driving the drive device based on an action command from a standard programmable logic controller, PLC, via a communication line and a feedback signal from the drive device, a drive signal path configured to transmit the drive signal from the drive signal generation circuit to the drive device, and a safety stop circuit configured to cut off the drive signal path when a stop instruction signal is input; and a drive signal generation circuit configured to generate a drive signal driving the drive device based on an action command from a standard programmable logic controller, PLC, via a communication line and a feedback signal from the drive device, a drive signal path configured to transmit the drive signal from the drive signal generation circuit to the drive device, and a safety stop circuit configured to cut off the drive signal path when a stop instruction signal is input; and a safety controller, configured to be directly connected with the safety driver by a control signal line, to generate a first stop instruction signal in response to an input of an operator using an input part, and to output the first stop instruction signal to the safety stop circuit of the safety driver, wherein the safety driver comprises a first external device monitoring, EDM, output part configured to detect a cutoff of the drive signal path by the safety stop circuit and to output a first EDM signal to the safety controller indicating that the drive signal path is cut off, the servo system being characterized by further comprising a safety communication unit, configured to be connected with the safety driver and the safety controller, to generate a second stop instruction signal in response to an instruction from a safety PLC via the communication line, and to output the second stop instruction signal to the safety stop circuit of the safety driver, wherein the safety communication unit comprises a second EDM output part configured to output a second EDM signal to the safety controller in a case where the safety stop circuit is activated according to the first stop instruction signal output from the safety controller, and not to output the second EDM signal to the safety controller in a case where the safety stop circuit is activated according to the second stop instruction signal.