We studied whether exercise fatigue affects somatosensory input using somatosensory evoked potential (SEP). Sixteen subjects performed intermittent grip strength exercises with muscle fatigue while ignoring electrical stimulation given to an elbow. We induced SEP in the exercise task (during contraction) in every stage (first stage, middle stage and final stage). In addition, we induced SEP in the exercise task during relaxation in the first stage and final stage. As a result, the early component amplitude of SEP decreased with the progress of exercise (manifestation of muscle fatigue) during contraction and relaxation. Our findings suggested that somatosensory input decreased with the manifestation of muscle fatigue. Somatosensory input is necessary for control of voluntary movement. Therefore, we speculate that these factors play a role in decreased performance of athletes competing in long -duration events.