This paper describes emotion-based walking for a biped humanoid robot. In this paper, three emotions, such as happiness, sadness and anger are considered. These emotions are expressed by the walking styles of the biped humanoid robot that are preset by the parameterization of its whole body motion. To keep its balance during the emotional expressions, the motion of the trunk is employed which is calculated by the compensatory motion control based on the motions of the head, arms and legs. We have constructed a biped humanoid robot, WABIAB-RII (WAseda BIpedal humANoid robot-Revised II), to explore the issue of the emotional walking motion for a smooth and natural communication. WABIAN-RII has forty-three mechanical degrees of freedom and four passive degrees of freedom. Its height is about 1.84 m and its total weight is 127 kg. Using WABIAN-RII, three emotion expressions are experimented by the biped walking, including the body motion, and evaluated.