A wearable device, comprising: a touch screen; a wireless communication unit configured to perform wireless communication with a mobile terminal; a sensor unit configured to sense at least one of a wearable device acceleration signal and a wearable device vibration signal; and a controller configured to: display a screen corresponding to an application executing on the wearable device, receive first state information indicating the at least one of the wearable device acceleration signal and the wearable device vibration signal, receive second state information from the mobile terminal indicating at least one of a mobile terminal acceleration signal and a mobile terminal vibration signal of the mobile terminal, and set one of the wearable device and the mobile terminal as an auxiliary device based on the first and second state information, wherein the auxiliary device performs an auxiliary function of the application in a state the application is executed in the wearable device and the mobile terminal, characterized in that the controller is further configured to display an enlarged user interface, UI, corresponding to a partial area of an application execution screen of an application being executed on the mobile terminal if the wearable device is set as the auxiliary device according to sensing the wearable device vibration signal. a touch screen; a wireless communication unit configured to perform wireless communication with a mobile terminal; a sensor unit configured to sense at least one of a wearable device acceleration signal and a wearable device vibration signal; and a controller configured to: display a screen corresponding to an application executing on the wearable device, receive first state information indicating the at least one of the wearable device acceleration signal and the wearable device vibration signal, receive second state information from the mobile terminal indicating at least one of a mobile terminal acceleration signal and a mobile terminal vibration signal of the mobile terminal, and set one of the wearable device and the mobile terminal as an auxiliary device based on the first and second state information, display a screen corresponding to an application executing on the wearable device, receive first state information indicating the at least one of the wearable device acceleration signal and the wearable device vibration signal, receive second state information from the mobile terminal indicating at least one of a mobile terminal acceleration signal and a mobile terminal vibration signal of the mobile terminal, and set one of the wearable device and the mobile terminal as an auxiliary device based on the first and second state information, wherein the auxiliary device performs an auxiliary function of the application in a state the application is executed in the wearable device and the mobile terminal, characterized in that the controller is further configured to display an enlarged user interface, UI, corresponding to a partial area of an application execution screen of an application being executed on the mobile terminal if the wearable device is set as the auxiliary device according to sensing the wearable device vibration signal.