Abstract: A cable-driven wrist mechanism for a robot arm which executes a rolling motion and a pitching motion, the wrist mechanism comprising: first and second motors provided in the robot arm; a first drive body rotated by the first motor; a second drive body placed above the first drive body, the second drive body being rotated by the second motor about a same rotating axis as that of the first drive body and independently with respect to the first drive body; a first rotary body rotated about a rotating shaft which is perpendicular to the rotating axis of the first drive body and located in a same plane as the rotating axis of the first drive body; a second rotary body having a rotating shaft same as the first rotary body, the second rotary body being symmetric to the first rotary body with respect to the rotating axis of the first drive body; a third rotary body connected to a sub-shaft which perpendicularly branches from the rotating shaft of the first and second rotary bodies, the third rotary body being symmetr