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 cover disposed on a rear side of the display, a detector configured to detect a user interaction on the display and the cover, and a controller configured to, in response to the display being folded along the folding line such that the first area and the second area face each other, control the detector to detect a user interaction through an exposure area, which is an exposed part of the second area, and the cover, and, in response to the display being folded such that the two parts of the cover face with each other with reference to the folding line, control the detector to detect a user interaction through the first area and the second area.