A method of controlling zoom of a lighting unit based on brightness of an image may include determining at least one of an angle of view of an optical unit and an optical zoom magnification of the optical unit configured to obtain an image by using an image sensor, determining a zoom adjustment range of a lighting unit based on at least one of the angle of view and the optical zoom magnification, and adjusting zoom of the lighting unit such that brightness of the image meets a preset condition within the zoom adjustment range, wherein a diffusion range of light from the lighting unit is adjusted through the zoom adjustment of the lighting unit.