According to one embodiment of a head up display according to an embodiment of the present invention includes a display information generating module which generates information that should be projected, a combiner which guides the information that is generated by the display information generating module and should be displayed to a predetermined position, a light adjustment control module which changes a transmitted light amount of the combiner based on brightness of a background and front image detecting module which detects brightness of the background to set the transmitted light amount of the combiner by using the light adjustment control module.