A quadruped walking robot, comprising a body part having a horizontal swing part, a horizontal swing drive part, an upper side upper leg part pivotally supported on the horizontal swing part, a lower side upper leg part disposed parallel with the lower part of the upper side upper leg part, an upper leg rotatingly driving part rotatingly driving the upper side upper leg part, a lower leg part having an upper end part to which the tip part of the upper side upper leg part and the tip part of the lower side upper leg part are pivotally connected on the upper and lower sides, and ground-contact part disposed at the lower end part of the lower leg part, and an elastic extensible part disposed at the middle part of the lower side upper leg part and elastically extending/retracting in the longitudinal direction.