A mobile telephone includes a casing provided with at least a locking member and a lid that can be detached or attached by pivoting of the locking member. The lid comprises a passage the locking member passes through, and a locking piece that a locking lug provided at the locking member can freely engage with and be detached from as a result of pivoting of the locking member. The locking piece is located at an inner periphery of the passage. Further, with a mobile telephone having casings that are foldably joined by a hinge, at least one of the foldably joined casings is a box-like case provided with a hinge at an upper surface and an opening portion at a rear surface, and has a lid-like case fitting to the opening of the box-like case.