This invention aims to achieve safety without interchanging an entire existing servo system to a servo system having the safety function. In a servo system including a servo motor, and a servo amplifier for controlling the drive of the servo motor based on the output of an encoder attached to the servo motor, a safety control device for monitoring presence of abnormality based on the output of the encoder, and shielding the supply of drive power to the servo motor if abnormality is present is arranged, and the monitoring content is set as setting information.