The purpose of this study was to investigate the influence of sensorimotor-cortex-response-based vibratory stimulation on stair climbing by the elderly and to reveal the functional assistance effect of vibratory stimulation. To do this, vibratory stimulation conditions (VSCs) were set through the reduction of the mu rhythm, an index of sensorimotor cortex excitability, and applied to elderly people during stair climbing. Joint angle, moment, power, and muscle co-activation (CA) of lower limbs were analyzed to investigate the influence of VSCs on stair climbing. As a result of vibratory stimulation, the biomechanical characteristics of the ankle and hip joints were further developed according to the VSC, and a tendency to compensate the knee joint work appeared. Also, functional improvement of the ankle joint was shown through greater energy transfer from the knee joint to the ankle joint. These results suggested that sensorimotor-cortex-response-based vibratory stimulation has the effect of functional assistance of the movement of elderly people and may be useful in research on movement assistance or rehabilitation for people with reduced body functions.