An upper case of the display section includes a first connecting portion having a cylindrical hole, into which an inner cylinder of a dummy hinge composed of two cylindrical portions having the same axis and different diameters is inserted rotatably, wherein the first connecting portion protrudes from an end of the upper case. An upper case of the keybutton section includes a second connecting portion located, along a hinge axis, on the center side of the first connecting portion, and having a cylindrical hole into which an outer cylindrical portion of the dummy hinge is inserted unrotatably, wherein the second connecting portion protrudes from an end of the upper case. The hinge structure comprises a stopper for fixing the dummy hinge, which can be inserted as the dummy hinge is buried in the cylindrical hole, with the inner cylindrical portion inserted into the cylindrical hole of the first connecting portion.