The invention has an object to provide a display device that enables a user to obtain information from a projection image without losing information obtained from the surrounding environment.The display device is to be mounted on a head of the user for allowing the user to view a predetermined image, and includes a light quantity detector (17) to detect a quantity of external light; a laser (211R, 211G, 211B) to emit a laser light having a light quantity depending on a current value; a light attenuator (22) including filters to switch an attenuation ratio so as to attenuate the laser light; an optical scanner (15) to scan the laser light transmitted through the filter; an optical projection system (16) to project the scanned laser light to form an image; and a controller (27) to control brightness of the image by increasing or decreasing the current value and by switching the attenuation ratio of the filter, based on the light quantity of the external light detected by the light quantity detector.