1. Three-dimensional (3D) glasses comprising: a transparent display unit displaying a control screen including a plurality of control icons for controlling an external 3D display device, on a 3D glasses unit; a transmission/reception unit receiving a signal related to the control screen including the plurality of control icons for controlling the external 3D display device from the external 3D display device; and a control unit controlling the transparent display unit to display the control screen corresponding to the received signal, which includes the plurality of control icons for controlling the external 3D display device.