A newly designed and developed head mounted display system, focusing on medical use for displaying images from an endoscope, reduces the burden of a doctor even during long, multiple-hour operations. In a conventional laparoscopic surgery, a doctor performs the operation while watching an external monitor. By wearing this head mounted monitor, 3D/2D endoscope images are shown on the display in front, meaning the operation can be performed in a free posture without being tied to the position of the external monitor. In addition to immersive 3D images, just moving the eyes a glance provides a perspective view of the part under operation to acquire any necessary information, which enables a smooth procedure. Now a new workflow can be proposed to doctors.