A Head Mount Display (HMD) and a method for controlling the HMD are disclosed. The method includes detecting an external device in an image captured by the HMD, recognizing at least one component from a first User Interface (UI) of the external device, the at least one component including a keypad or a window for outputting data corresponding to an input signal to the keypad, generating a second UI including the recognized at least one component, displaying the second UI in the HMD, wherein the at least one component of the first UI being displayed on the external device is overlaid with the displayed second UI using the image from which the external device is detected, and displaying data corresponding to an input signal currently received at the external device on the second UI in the HMD.