A control device is provided with a communication unit and a processing unit. The communication unit makes communication with a tool that is used for the work of fastening a fastener (for example, a screw) and with an image pickup unit for capturing an image of the work site where the work is being performed. The processing unit executes a determination process of determining whether or not the work is being performed normally on the basis of the fastening torque applied to the fastener by the tool and the image captured by the image pickup unit.