A robot arm for industrial robots comprises one or several jointed arms (1,1c) that are mutually connected to each other by means of rotary joints (1a, 1b), and a jointed arm (1) connected to a base (3), in which an angle transducer is arranged in the rotary joints (1a,1b) in order to measure exactly the angular relationship between the jointed arms (1,1c) or between the jointed arm (1) and the base (3), in order to make possible adjustment of the robot arm into the desired angular position.