A head-mounted display (HMD) that enables a wearer to favorably view and recognize images even in a very bright environment, has a HMD in which image display light emitted from a display element is guided to an eye of an observer via a visor, whereby a virtual image of an observed subject is formed in front of the observer. In the HMD, light source devices are a first light source, outputting light of a high intensity, and a second light source, outputting light of a. low intensity. The light source devices have a switch to switch between the first and second light sources. The display element, the visor and the second light source are attached to a mount, worn on the head of the observer. The first light source is installed in a moveable body with the observer, and is connected to the mount via light transmission paths.