PURPOSE: To provide a case structure wherein the mounting operation of a coupling member can be performed simply.

CONSTITUTION: The case structure is composed of a lower-part case 2, of an upper-part case 1 which is attached to the lower-part case 2 so as to be capable of being opened and shut by 4 coupling pin 23, of an upper-part back lid 5 which is attached to the rear surface of the upper-part case 1 and of a coupling member 31 which is pressed and fixed to a mounting recessed part 30 in the rear surface of the upper-part case 1 by the upper-part back lid 5, by which a hook part 32 is inserted into a coupling hole 32 in the lower-part case 2 when the upper-part case 1 is closed and which is coupled to a coupling protruding part 34 inside the coupling hole 33 so as to be capable of being coupled and detached. Then, when the upper-part back lid 5 is attached to the rear surface of the upper-part case 1, the coupling member 31 is attached simultaneously.