We are trying to induce a quadruped robot to walk dynamically on irregular terrain by using a neural system model. In this paper, we integrate several reflexes such as stretch reflex, vestibulospinal reflex, and extensor and flexor reflex into CPG (Central Pattern Generator). The success in walking on terrain of medium degree o] irregularity with fixed parameters of CPG and reflexes shows that the biologically inspired control proposed in this study has an ability ]or autonomous adaptation to unknown irregular terrain. MPEG footage o] these experiments can be seen at: http ://www.kimura.is. uec.ac.jp.