A mobile device includes a first housing and a second housing. The first housing includes a first track surface parallel to a first direction, and a first housing first flat surface perpendicular to the first direction. The second housing includes a first pin, and a second housing first flat surface facing to the first housing first flat surface. The first pin protrudes from the second housing first flat surface. The second housing first flat surface slides along the first housing first flat surface, and the first pin slides along the first track surface, therefore the second housing slides with respect to the first housing. The mobile device is provided, in which smooth sliding without backlash is possible.