To easily assemble a coffin at the site of use by forming side plates by sticking the frame wood to bar wood of particle materials having specified thickness by sandwiching them between fiber boards having specified thickness, connecting and fixing the respective side plates and a floor plate through plastic juggles.

In an assemblable fiber board coffin 50, side plates 5a-5d are formed by sticking frame wood 1a-1d to bar wood 2a-2d of particle materials having thickness from 10mm to 20mm by sandwiching them between fiber boards 3a and 3b having thickness from 2mm to 3mm. Then, a window hole 6 and a door 8 fitted through a plastic hinge 7 to the window hole 6 are provided. Further, this coffin is provided with an upper plate 10 equipped with a matching bar 9, floor plate 15 having a structure filling the closed space formed between the fiber boards with the medium-gravity fiber honeycomb materials of honeycomb structure, plastic nails for fixing the upper plate 10, and plastic juggles for connecting and fixing the respective side plates 5a-5d surrounding four faces with the floor plate 15. Thus, the strength of floor plate can be improved while keeping it light in weight.