Psychophysiological indexes based on questionnaire scores and heart rate variability analysis are widely used as mental health indexes. In this study, we focused on respiratory information and aimed to explore respiratory parameters related to psychophysiological indexes of mental health. Seven respiratory parameters were used: respiratory rate, inhalation time, exhalation time, exhalation-inhalation ratio, inhalation time variability, exhalation time variability, and exhalation-inhalation ratio variability. Furthermore, the seven respiratory parameters were analyzed using representative psychophysiological indexes: relaxation scale, anxiety scale (STAI), sleep scale (PSQI-J), and pulse wave, EEG. Twenty-eight university students participated in the experiment. Simultaneous measurements with a band-type respiration sensor, an optical pulse wave sensor, and an electrode-type EEG sensor were performed for 5 min in a resting state after obtaining answers to each questionnaire, and finally, answers to the questionnaires were obtained again. A correlation analysis of the respiratory parameters and psychophysiological indexes revealed a positive correlation (r=0.41 and r=0.44, respectively) between state anxiety and the variability of inhalation and exhalation times (p<0.05). This result suggests that the variability of inhalation and exhalation times can potentially be used for mental health assessment.