Control device of robot arm and teaching system and method using the same

A control device of robot arm including a pressure sensing module and a control module is provided. The pressure sensing module, disposed on an operating portion of a robot arm, has a touch-sensing surface for detecting an operation command applied to the touch-sensing surface. The control module receives at least a pressure sensing signal outputted by the pressure sensing module and outputs a motor driving signal to the robot arm in response to the operation command. The touch-sensing surface includes a first touch-sensing region and a second touch-sensing region. The first touch-sensing region is for defining a first reference coordinate system satisfying a translational motion mode. The second touch-sensing region is for defining a second reference coordinate system satisfying a rotational motion mode. The control module controls the robot arm according to the operation command.