There is a variety of therapeutic modality for herniated nucleus pulposus. Recently the low level laser has come into use for treatment for it. We treated two patients suffered from herniated nucleus pulposus of the central type of $L_{3,4}$ level, with He-Ne, $CO_2$ and Ga Al As laser simultaneously daily under hospitalization. In order to determine the efficacy of treatment, we used the "visual analogue scale" and its improvement rate. The results were as follows; Case I complained of gait disturbance, and hypoesthesia on the lateral side of the left lower leg, as and as low back pain. At the 15th day after treatment, VAS improvement rate was 40%, and the gait disturbance and hypoesthesia were markedly improved. 35th days after tratement, VAS improvement rate was 80%. Case II complained only of low back pain. At the 15th day after treatment, the VAS improvement rate was 68%, and at 20 days after treatment it was 84%. We sugsest that, using the low level laser for treatment of herniated nucleus pulposus increased the cartilage entrophism, and inhibitory effects of the inflammatory materials such as acid glycosaminoglycan by its anti-inflammatory and analgesic effects.