A robot arm calibration device is provided, which includes a light emitter, a light sensing module, a cooperative motion controller and a processing module. The light emitter is disposed on at least one robot arm to emit a light beam. The light sensing module is disposed on at least another robot arm to receive the light beam and the light beam is converted into a plurality of image data. The cooperative motion controller is configured to drive the light emitter and light sensing module on at least two robot arms to a corrected position and a position to be corrected, respectively. The processing module receives the image data and the motion parameters of the at least two robot arms to calculate an error value between the corrected position and the position to be corrected, and analyzes the image data to output a corrected motion parameter for modifying motion command.