To improve the production capacity in a work process, while reducing the number of defective products generated in the work process with regard to works.

When a forgetfulness of fastening a screw such as removing the work from a work table 30 is caused before completing screw fastening work to a work W by a motor-driven driver 1, a buzzer arranged inside an electric power supply device 10 issues a warning sound. An arithmetic processing part inside of the electric power supply device displays the miss ratio and a miss frequency of a worker on a liquid crystal display 16 on the basis of a count value, by counting a cumulative frequency of causing the forgetfulness of fastening the screw with every worker. Thus, work can be performed while arousing attention to the worker.