An electronic device having a first housing including a first surface and a second surface at a rear surface opposite of the first surface and a coupling structure disposed on the first surface. A second housing for coupling to the first housing has a third surface, a fourth surface opposite of the third surface, and a side member enclosing a space between the third and fourth surfaces. The coupling structure is connected to the side member when the second housing is coupled to the first housing, and the coupling structure comprises a recess and a moving member. When the second housing is coupled to the first housing, the moving member performs a pivotal movement about a shaft. A retainer system may enable the second housing to at least partially stay within the moving member at the recess when the second housing is not coupled to the first housing.