To provide a head mount display device which dispenses with periodical calibration and is capable of suppressing the increase in weight of a helmet.

The head mount display device which has a display screen provided on a helmet of a user and detects his or her head position and attitude to display images around the device, which are photographed by cameras, meter symbols, etc. in accordance with detection outputs, includes a plurality of markers arranged on the helmet and a plurality of cameras fixed to the periphery of the helmet. The markers are photographed by the cameras to discriminate directions and classifications of the markers, therby the head position and attitude are detected.