A head-mounted display system may include a display device and a head-mounted device. The display device includes a touch screen surface exposed to an outside and including an active region which displays an image and senses a user input. The head-mounted device includes a frame, in which a reception space allowing the display device to be mounted therein is defined, and an optical system disposed in the frame. The active region of the display device includes a first active region, which is exposed to the outside and receives the user input for controlling the head-mounted device, when the display device is coupled with the head-mounted device.