A joining structure of superposed first to fourth segment housing of an electronic device each having a display screen equipped with two shafts arranged between first and second housing segments and third and fourth housing segments, a first hinge which joins end faces of the second and third housing segments to be able to rotate and a second hinge which joins opposite side end faces of the first and fourth housing segments, two shafts make the second and third housing segments slide with respect to the first and fourth housing segments, then make one rotate 180 degrees with respect to the other in the finished slid state, by using the first and second hinges to make the second and third housing segments and the first and fourth housing segments rotate about the shafts, and superposed first to fourth segment housing are opened to form a single flat display surface.