In this paper, a robot arm capable of recognizing and drawing various line thicknesses is developed. Conventional line drawing robots are not capable of adjusting the thickness of lines. However, to draw faster and to enrich the expression of line drawing robots, it is necessary to adjust line thickness using a brush pen. Simple images are acquired and various line thicknesses are recognized by image processing. Trajectories of lines are generated with distance sorting using thinning and corner point detections for each label. Information on line thickness and trajectory is sent to the controller of a robot arm taking into consideration 2D inverse kinematics. Through this process, the robot arm can draw various lines thicknesses along 2D trajectories with 3 motors. Robot arm for detailed drawing will be studied in the future.