Provided is a wearable electronic device which may adjust the transmittance of a visor and the intensity of a display. According to various example embodiments, a wearable electronic device may include a visor adjusting the amount of external light entering a user's eyes depending on a transmittance, a display outputting the light projected on the user's eyes through an optical waveguide, a camera capturing an image of the user's eyes, and a processor tracking the user's gaze direction from the image of the user's eyes and supplying a control signal to the visor and the display, wherein the processor may determine the transmittance of the visor and the intensity of light output from the display.