Abstract: A hand-eye calibration method and a hand-eye calibration device for a robot arm are provided. The method includes following steps. A first mapping relationship between a base of the robot arm and a terminal of the robot arm and a second mapping relationship between a camera and a target object are obtained. Based on a scale, a third mapping relationship between the terminal of the robot arm and a tool set mounted on the terminal and a fourth mapping relationship between the camera and the base in each dimension are updated to minimize an error between a position of the target object in an image captured by the camera and a position of the tool set. In response to the error being convergent and the scale being less than or equal to a scale threshold, the third mapping relationship and the fourth mapping relationship calibrated by the scale are output.