To provide a coffin which is changeable into a desired design without moving the coffined remains from coffin to coffin and in which kinds of handleable coffins are increased without restriction of keeping places.

The coffin is assembled and prepared by mounting L-shaped mauls with inserting grooves worked mounted on three sides of each of four front, rear, left, and right lateral sides of a coffin body except for the bottom and mounting a maul having an opening on one remaining side. A plate worked into size to cover the four lateral sides is inserted to each opening. Next, a plate worked into size to cover an upper lid portion is inserted to an upper lid with an L-shaped maul with inserting grooves worked on its three sides mounted thereon. Grooved L-shaped mauls of the same specification as the mauls cut corresponding to the size of the opening are mounted over the opening by fastening two or three screws, drive nails or using adhesives or double-sided adhesive tapes and the openings are closed to complete the coffin. The design of the coffin is prepared by being applied to the inserting plates before inserting the inserting plates to the mauls.