An artificial knee joint, which includes an upper surface at which a post performs a motion relative to a cam of the thighbone coupling member, is configured such that a radius of curvature of an upper curved surface extending posteriorly from the upper surface is larger than that of a lower curved surface, so as to prevent the cam of the thighbone coupling member from deviating from an inflection point existing between the upper curved surface and the lower curved surface, and is configured such that the upper surface is inclined at a predetermined angle, so as to allow the thighbone coupling member to be restored while naturally descending along the upper surface even when the thighbone coupling member is dislocated, thereby increasing a jump distance without increasing an amount of bone to be cut.