The bean bug, Riptortus clavatus(Thunberg), is an important soybean pest in Japan. Since both adults and nymphs are sucking soybean pods, the damage is often serious even their population density is low. Therefore, it is necessary to observe the bug population in the soybean field to reduce the damage. To save labor for monitoring the occurrence of the pest, we used automatic counting traps, ‘altered MUSHIDAS 2000’ baited with synthetic attractants identified by Leal et al. (1995). This automatic counting trap, originally designed for Lepidopteran pests baited with synthetic sex pheromones, utilizes a solar battery to work continuously and sends data automatically via a built-in mobile phone. The occurrence of the bugs was also monitored by three water-pan traps. The number of bugs counted automatically and the actual numbers of catches in the automatic counting trap were not always consistent. One of the reasons for this inconsistency might be due to that the current automatic counting trap could not eject clogged insects in a roller electrode, which worked for detection of the bugs. However, the number of seasonal catches by automatic counting and water-pan traps showed similar trends, and the catch numbers of these traps reached a peak around the same time, in October. Although the automatic counting trap needs improvement, it should be useful for investigating the occurrence of the bean bug population utilizing less labor.