Abstract: An electronic apparatus, an image capturing device and a method for automatically capturing an image thereof are disclosed. The image capturing device comprises an image capturing module, a sensing module and a processing module. The image capturing module is used to capture an image corresponding to a scene through a capturing window. The sensing module senses a brightness value of the scene. The processing module is used to divide the capturing window into a plurality of blocks, and control the sensing module to decide whether the brightness value of each block has been changed. When the brightness value of any block has been changed, the processing module controls the image capturing module to capture the image.