Abstract: The present invention provides a pointing device comprising a housing, a roller ball module and a circuit board. The roller ball module has a mounting frame detachably installed in the housing, a roller ball rotatably fixed in the mounting frame and two light gratings rotatably installed in the mounting frame for contacting the roller ball to detect rotations of the roller ball in two different directions. The circuit board installed in the housing has two optic sensors for sensing rotations of the two light gratings and generating corresponding two-dimensional pointing signals. The roller ball module can be attached to or detached from the housing directly by hand.