A prototype HMD which can automatically adjust interocular distance in the range of 55 mm to 75 mm in accordance with those of users. The main component of the HMD is a linear motor which shifts the modularized left and right eye’s projection and camera optics in accordance with the measured interocular distance of a user. The total adjusting time of the distance is less than 10 seconds. The weight of the HMD is slightly less than 500 g and it is worn by a head belt. The HMD is somewhat heavy and unbalanced due to the distribution of the weight along the nose side but the head belt holds tightly the HMD on its place and it works well.