To provide a biped walking robot and its control method, in which both legs do not interfere with each other even when errors occur in the position of right and left legs in an actual operation with respect to the trajectory data of the right and left legs previously predicted.

The closest estimated distance δ0 between the right leg F1 and the left leg F2 in the case when the right leg F1 and the left leg F2 approach most is calculated by predicting it based on the trajectory data. The actual measuring distance between a sensor disposed on one leg and the other leg is calculated by the sensors (S11, S12, S21, S22) disposed on at least one of the right leg F1 and the left right leg F2, and the closest distance δ1 between the right leg F1 and the left leg F2 is calculated from the actual measuring distance. When the closest distance δ1 is shorter than the closest estimated distance δ0, the trajectory data is corrected, and walking is performed by alternately changing the right leg F1 and the left leg F2 to a standing leg and an idle leg according to the corrected trajectory data.