To provide an environment protective coffin structure which is formed by folding cardboards to increase the thickness.

One box body is formed by folding and combining plural cardboards, which constitute a bottom board, frame board, reinforcing board, strengthening board, inner bottom board, inner lid board, outer lid board and ornamental lie board. Four peripheral faces are formed by folding the frame board. The bottom board is formed by combining the reinforcing board and the peripheral strengthening bard inside and folding them on the base of the frame board. The inner bottom board of a single layer is fitted to the inner surface of the frame board. The lid body is formed by folding and combining the inner and outer lid boards, the inner lid board of which is folded and has a comparatively large inward protruding peripheral edge and is locked on the inside of the upper edge of the box body, the outer lid board of which is folded and has a comparatively small inward protruding peripheral edge and is combined on the upper edge of the box body. The ornamental board folded with four conical sides is stuck to the upper surface of the outer lid board.