A displacement detection device includes an image sensor, a processing unit and an output unit. The image sensor is configured to detect reflected light from a working surface to successively output image frames. The processing unit is configured to identify a hovering height and calculate a first axis displacement and a second axis displacement according to the image frames. The output unit is controlled by the processing unit to output a first ratio of the first axis displacement but not to output the second axis displacement when the hovering height is higher than a predetermined height.