PURPOSE: To simply and inexpensively manufacture the case of an arbitrary shape by preparing the cover part of a case and both edge parts of a main body part and connecting them with a desired shaped intermediate member.

CONSTITUTION: Intermediate members 41 and 42 having a shape determined based on the length of a releasing direction to open a cover part 100 and the thickness of a case are manufactured. Locking parts 13 and 14 to lock in the condition to close the cover part 100 and a main body 101 and hinge parts 5 and 6 to connect the cover part 100 and the main body part 101 are equipped, both edge members 1W4 to constitute both edge parts of the cover part 100 and the main body part 101 and the intermediate members 41 and 42 corresponding to both edge members 1W4 are connected, a case is formed and the intermediate members 41 and 42 are exchanged. Thus, the case of various shapes can be manufactured simply and inexpensively.