There is provided a replaceable sliding cover unit for a folder-type phone having a main body, a folder, and a hinge device for connecting the folder to the main body rotatably. A slot is formed around the periphery of the folder. A replaceable sliding cover, having a window at a predetermined position, is mounted along the slot to cover the upper portion of a folder case and detachable from the folder by sliding in the length direction of the folder-type phone. A raised edge and a locking unit fixes the cover in the slot.