This paper describes the development of equipment to detect alcohol in the human body. When drivers want to switch the engine on by the ignition-key, the equipment judges whether or not they have drunk alcohol. The theorem of the equipment to detect is based on the electrodermal activity. The comparison between the method and two kinds of equipment of breath alcohol detections on the market is performed. Their equipment has shown the higher level just after drinking alcohol, but they reveal lower levels when time has passed of drivers who were drunk. On the other hand, the method shows the same events of the values and questionnaires of volunteers.