[Purpose] The purpose of this study was to compare the effect of humidity changes on the values of pulmonary function at rest. [Subjects and Methods] This study was conducted with 30 young adults (9 males, 21 females; mean age 19.4 years). Participants’ mean height was 165.1 cm, and their mean weight was 60.2 kg. The experimental setting was a laboratory in which temperature was fixed at 25 °C. Using a humidifier, relative humidity was successively to adjusted 25%, 50%, and 90%, and pulmonary were measured functions at each level. Using a spirometer, forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), expiratory reserve volume (ERV), and tidal volume (TV) were measured, and the results were compared and analyzed. [Results] Controlling for temperature, FVC and FEV₁ showed statistically significant differences among different levels of relative humidity, but FEV₁/FVC, TV, and ERV showed no significant difference. [Conclusion] In the case of exercises that require large respiration volumes, such as aerobic exercises or exercise load tests, it is recommended that higher than normal humidity levels should be maintained.