An automated replacement device moves in a right-left direction along a front surface of production line including multiple machines. The automated replacement device moves to a front side of an instructed machine among the multiple machines to perform an automated replacement operation on the machine. A periphery monitoring device monitors a safety area set in a periphery of the automated replacement device to stop an operation of the automated replacement device in an emergency manner when a person or an obstacle is detected in the safety area and alarm device sounds an alarm to notify that the automated replacement device is moving, in which the periphery monitoring device is switched such that a range of the safety area during the movement of the automated replacement device is smaller than a range of the safety area during the automated replacement operation.