An automatic jig replacement system includes a detection device, a robot, a bolt tightening/loosening device, and a control device. The detection device is configured to be capable of detecting a predetermined part of a jig. The robot is configured to be capable of conveying the jig. The bolt tightening/loosening device is configured to be capable of tightening/loosening a bolt for securing the jig. The control device determines a bolt tightening/loosening position, on the basis of a result of detecting the predetermined part by the detection device. The robot is caused to unload the jig from the mounting position, or to load the jig to the mounting position. The bolt tightening/loosening device is moved to the bolt tightening/loosening position, and is caused to tighten or loosen the bolt.