Disclosed are a mobile device and controlling method thereof. The present invention includes a memory configured to register a first iris image, an illumination sensor configured to sense an external illuminance of the mobile device, a display configured to emit a light from a preset region, a camera configured to detect either a second iris image or a pupil image, and a controller configured to control the memory, the illumination sensor, the camera and the display and control the display to display a message for guiding a change of an eye according to the external illuminance sensed by the illumination sensor, wherein the message for guiding the change of the eye is changed according to the sensed external illuminance.