There is provided a displacement detection device including an image sensor, a light source, a light control unit and a processing unit. The image sensor captures image frames at a sampling frequency. The light source provides, in a speed mode, light for the image sensor in capturing the image frames. The light control unit controls the light source with the speed mode to turn on at a lighting frequency or to turn off serially. The processing unit calculates a displacement according to the image frames captured when the light source turns on to be served as an estimated displacement for an interval during which the light source turns off. There is further provided an operating method of a displacement detection device.