Abstract: We experimentally used software that enables the acquisition of information of heart rate from video sources, in the expectation that we can utilize it to monitor students' mental states in the classes, for example, the online class using video-conference systems. We observed that this system works well, and we can utilize the information of students' mental state if the student stayed still and make no movements in front of the camera for a while, but some restriction on movements will be necessary for the acquisition of biometric data if we use this kind of software/system in the classroom practices. The acquisition and utilization of this kind include the problems of operation and privacy.