A user terminal device and a controlling method thereof are provided. The user terminal device includes a display configured to be divided into a first area and a second area which is larger than the first area with reference to a folding line, a detector configured to detect a user interaction, and a controller configured to, in response to a folding of the display with reference to the folding line being detected through the detector, control the display to display a predetermined UI on an exposure area which is exposed part of the second area.