A mobile terminal comprising: a body; a communication unit configured to externally transmit and receive a signal; an input unit configured to receive user input; a display coupled to the body to vary a display region viewed from a front face of the body according to switching between an enlarged display mode and a reduced display mode; whereby the body includes a first frame and a second frame, and the second frame is extendable and contractible from the first frame, and the mobile device operates in an enlarged display mode as the second frame is extended, and operates in a reduced display mode as the second frame is contracted; and a controller, wherein the controller is configured to: output a first application on the display, while the display is in the reduced display mode, output a message pop-up window and a button both corresponding to a notification corresponding to a second application upon receiving the notification while the first application is being output on the display in the reduced display mode, receive a first signal corresponding to touch selecting the button, output a preview pop-up window for the second application while the first signal is maintained, and when a dragged distance according to the first signal exceeds a first threshold value, switch the display from the reduced display mode to the enlarged display mode and then output the first application in a first region of the display in the enlarged display mode and output the second application in a second region of the display in the enlarged mode. a body; a communication unit configured to externally transmit and receive a signal; an input unit configured to receive user input; a display coupled to the body to vary a display region viewed from a front face of the body according to switching between an enlarged display mode and a reduced display mode; whereby the body includes a first frame and a second frame, and the second frame is extendable and contractible from the first frame, and the mobile device operates in an enlarged display mode as the second frame is extended, and operates in a reduced display mode as the second frame is contracted; and a controller, wherein the controller is configured to: output a first application on the display, while the display is in the reduced display mode, output a message pop-up window and a button both corresponding to a notification corresponding to a second application upon receiving the notification while the first application is being output on the display in the reduced display mode, receive a first signal corresponding to touch selecting the button, output a preview pop-up window for the second application while the first signal is maintained, and when a dragged distance according to the first signal exceeds a first threshold value, switch the display from the reduced display mode to the enlarged display mode and then output the first application in a first region of the display in the enlarged display mode and output the second application in a second region of the display in the enlarged mode. output a first application on the display, while the display is in the reduced display mode, output a message pop-up window and a button both corresponding to a notification corresponding to a second application upon receiving the notification while the first application is being output on the display in the reduced display mode, receive a first signal corresponding to touch selecting the button, output a preview pop-up window for the second application while the first signal is maintained, and when a dragged distance according to the first signal exceeds a first threshold value, switch the display from the reduced display mode to the enlarged display mode and then output the first application in a first region of the display in the enlarged display mode and output the second application in a second region of the display in the enlarged mode.