A screwdriver is connected to an electric power supply, and rotates a mounted bit to tighten a screw. The screwdriver includes a camera, an image information recording section, a basic information registration section, a determination section, and an LED unit. The camera captures the screw to be tightened or surroundings of a threaded hole in which the screw is to be tightened. The recording section records an image captured by the camera. The registration section registers beforehand image information, which has been acquired by capturing with the camera an image of the surroundings of the threaded hole, as basic information. The determination section determines whether or not new image information, which has been newly acquired by capturing an image of the surroundings of the threaded hole with the camera, coincides with the basic information. The LED unit notifies a result of determination by the determination section.