The reduction of communication opportunities between students in online classes under the COVID-19 pandemic has been identified as a problem. Although student communication in online classes is said to have a positive effect on students' mental state, there have been no research that have compared the effectiveness of different forms of communication. In addition, there is a need for more objective evaluations. We therefore purpose to objectively evaluate the effect of each form of communication in online classes on the mental state of students. We propose to divide the forms of communication in online classes into five levels and to use biometric information. There was a tendency to relax at higher levels of communication and higher levels of concentration at medium levels of communication.