Purpose : The purpose of this study was to investigate the change of the peak plantar pressure distribution under the foot areas and the range of motion (ROM) of ankle joint according to gradients in treadmill gait. Method : Thirty normal subjects (15 male and 15 female) walked on treadmill at three gradient conditions ($0^{circ}$, $10^{circ}$, and $15^{circ}$) in normal speed. The ankle ROM was measured using the CMS70P that is three dimensional analyzer for excursion of ankle ROM, plantar flexion, and dorsi flexion. The peak plantar pressure distribution under the hallux, 1st metatarsal head (MTH) and heel was measured using the F -Scan system with an in-shoe sensor. Data was collected from 9 steps of left sife foot in at each gradient condition while all subjects walked. Result : As the treadmill gradient increased, the excursion of ankle joint was significantly increased (p<.05). Also, plantar flexion and dorsi flexion was significantly increased according to treadmill gradients (p<.05). The peak plantar pressure under the 1st MTH was significantly increased (p<.05) and the peak plantar pressure under the heel was significantly decreased (p<.05) as the treadmill gradient increased. No significant different in the peak plantar pressure under the hallux was observed. Conclusion : This study suggests that physical therapy for patients who have limited ankle ROM should be considered sufficient range of motion for functional ambulation. And individuals that have painful forefoot syndromes, including metatarsalgia, hallux valgus, and plantar ulceration should be careful in walking to uphill, as there is high plantar pressure under the forefoot.