To provide a jaw flaccidity preventing device for dead bodies for easily and reliably preventing a mouth from opening when muscles of a jaw part become flaccid after death.

The jaw flaccidity preventing device 1 for dead bodies includes a horizontal plate-like part 3 for covering at least molar teeth of a dead body and a joining member 2 having at least one wall part 5 which is formed to be perpendicular to the plate-like part and is provided on a side surface of the molar teeth, and has adhesive agent layers 7 which are formed on surfaces, making contact with the molar teeth, of upper and lower surfaces at least of the plate-like part to stick upper and lower tooth rows together by the adhesive agent for preventing the mouth from opening owing to the flaccidity of the jaw. In a preferred form, at least one through-hole 4 is formed in the plate-like part. Further preferably, the plate-like part and a pair of the right and left joining members 2 having at least one wall part formed to be perpendicular to the plate-like part are integrally connected by an elastic connecting part 6 bent into a U shape. Preferably, the adhesive layer is formed on a surface, which makes contact with the molar teeth, on the wall part.