The balance adjustments play an important role in orthostatic and dynamic postural control, influencing the ability to perform daily living and sports activities in preventing injuries and improving performances. And a stomatognathic system thought to be involved in postural control. However, the relation between stomatognathic system and the equilibrium function has not been made sufficiently explicit. The purpose of this study was to investigate an effect of an experimentally altering mandibular position on equilibrium using a planar inclination of body and fluctuation in centerof- foot pressure in orthostatic postureanda stepping test. Twelve healthy males (32.45 ± 9.2 years of age) participated as subjects. Rotation angle, transfer angle and transfer distance during the stepping test, and planar inclinations of the body and path length in center-of-foot pressure were determined at before stepping test, using force plates and the VICON motion capture system. Deviation and rest splints were fabricated using soft-and-hard double-layer sheets pressure formed on maxillary and mandibular models: the former was positioned at the edge of the upper and lower canines where they came into contact on the non-habitual chewing side; the latter was positioned at the mandibular rest position. Significantly greater inclination of the cranial, shoulder and pelvic planes and path length in center-of-foot pressure were observed with the deviation splint. And significant increases were observed in rotation angle, transfer distance, and transfer angle with the deviation splint compared with the rest position or with the rest splint. Within the limitations of this study, these results suggest that even the alteration in mandibular position affects equilibrium function.