Abstract: A door with a display unit mounted therein. This display unit has: a first substrate; a driving circuit on the first substrate; a display device on the driving circuit; a second substrate on the display device; and a door knob on the first substrate and the second substrate. The display unit is configured to display at least one of an individual identification code, a current state of usage, current user information, a duration of use, next user information, and current time information of a predetermined space.