This paper proposes a walking trajectory modification with a gyroscope for biped robots on uneven terrain. Many researchers proposed adaptation methods to uneven terrain for biped robots, such as adaptable mechanisms, compliance controls, etc. However, these methods have a limit in adaptation, and they cannot adapt on uneven terrain in some situations e.g., high bumps. In this paper, the walking trajectory modification for adaptation on uneven terrain is proposed. The proposed method is used with controllers for adapting to uneven terrain. The walking trajectory modification compensates the error that cannot be completely compensated by the controller. By using the proposed method, biped robots can walk on uneven terrain that exists unknown high bumps. The validity of the proposed method is confirmed by experiments.