The invention discloses a head-mounted display device and method for automatically measuring pupil distance. The head-mounted display device comprises a frame, two eye lenses, two photographic devices, two lighting devices and an image processing module. The two eye lenses are mounted symmetrically on the side, directly facing a user, of the frame. The two photographic devices are mounted symmetrically on the frame, the two photographic devices are separately located on the outer sides of the two eye lenses, and lenses of the two photographic devices are located outside the frame and face eyesof the user. The two lighting devices are mounted symmetrically on the frame, and the two lighting devices are separately located on the outer sides of the two eye lenses. The photographic devices are separately connected with the image processing module. The method for automatically measuring the pupil distance relies on the head-mounted display device, and a two-dimensional space calibration method is used for measuring the pupil distance. The device is simple in structure and easy to operate. The head-mounted display is simple in structure and convenient to operate. The method for automatically measuring the pupil distance has high precision and accuracy.