The method of a portable device may includes the steps of setting a first mode based on a first folding angle between the first body and the second body and a second folding angle between the first body and the third body, displaying a first application in the first mode, detecting change of the first folding angle and change of the second folding angle in the first mode, detecting the changed first folding angle being equal to or greater than a first threshold angle and the changed second folding angle less than a second threshold angle and if it is detected that a rear side of the second body is in a state of being contacted with a different real object, switching the first mode to a second mode.