A device for compensating the weight of a robot arm of a robot with a spring cylinder and having at least one helical spring is characterized in that there is at least one mechanism for the insertion and removal of at least one further, replaceable helical spring and preferably a pretension of at least the replaceable helical spring is adjustable. The device according to the invention makes it possible to modify the spring constant of the spring cylinder in order to individually adjust the compensating force desired for compensating the weight of the robot.