The purpose of this paper is to investigate the usage of address terms for professors by undergraduate and graduate students by the sociolinguistic methodology. To this end, this paper applied an integrated approach that combines quantitative analysis based on the response results of multiple-choice questions in the survey and qualitative interpretation based on the response results of subjective questions in both the survey and the in-depth interview. First, through quantitative analysis of the variation in the use of address terms, it was confirmed that “professor” occupies an overwhelming proportion and that the academic field of the speaker is the most important factor. The higher the intimacy with professors, the more “teacher” was used. Next, through the qualitative interpretation of the reason and meaning of using their choice of address terms, the most basic and superficial reason was to follow the experiences and customs in the affiliated community. The use of “professor” had some reasons or meanings such as meeting courtesy and expectations, highlighting privileged status, and equal respect for all the faculty members, whereas “teacher” was used as an expression of intimacy.