A portable electronic device includes a first housing: a second housing coupled with the first housing such that the second housing can slide while facing the first housing, guide ribs arranged on the first housing, guide slits arranged on the second housing, and at least one protuberance arranged on either an outer surface of each guide rib and an inner wall of each guide slit. The guide slits extend along a direction in which the second housing slides and each guide rib is restricted in each guide slit so as to guide a sliding movement of the second housing. The at least one protuberance contacts either an inner wall of each guide slit or an outer surface of each guide rib.