A method of controlling a head mounted display (HMD) device according to one embodiment of the present specification includes the steps of detecting whether the head mounted display device is in a wearing mode or a non-wearing mode, if the head mounted display device is in the wearing mode, displaying the digital information with a first user interface format, and if the head mounted display device is in the non-wearing mode, displaying the digital information with a second user interface format, wherein the digital information displayed with the second user interface format corresponds to the digital information displayed in a manner of expanding the digital information displayed with the first user interface format.