The purpose of this study is to investigate and analysis effect of TENS with immunohistochemistry methode through changes of substance P in spinal using arthritis model after inducing inflammation. The changes of substance P induced at that time are compared with control which is not induced arthritis by means of counting. The effect of TENS (4Hz, $200{mu}$, 20minutes) is also tested by observing changes of substance P in spinal dorsal horn after application on knee joint of rats which is arthritis model induced by kaolin and carrageenan. The results of this study were as follows: 1. Substance P immunoreactive positive neurons are increased in dorsal horn after inducting arthritis. 2. In arthritis group, Substance P immunoreactive positive neurons are progressively increased from the first to the third days. 3. Substance P immunoreactive positive neurons after applicating TENS on arthritis group are more decreased than only arthritis-induced group. 4. Substance P immunoreactive positive neurons were significantly decreased on the second days resulting from TENS application from the first to the third days. Therefore, TENS application is decrease Substance P immunoreactive positive neurons in spinal dorsal horn of rats induced arthritis. This decrease is considered as analgesic effect of TENS.