To provide a mat for sleeping face down which is spread under a body of a user when he or she lies on his or her stomach, stabilizes his or her body and reliably prevents his or her chest, back or the like from being damaged.

The mat for sleeping face down is formed into a flat shape whose long side has a length (a) corresponding to the part from the neck to the upper part of the sidebone and whose short side has a length (b) corresponding to the shoulder width when it is spread. It has an upper layer part 1 which exhibits resilience and a relatively low compression deformability and a lower layer part 2 which exhibits resilience and a relatively high compression deformability. The upper layer part 1 has compression deformability to such a degree that one end in the direction of its length can lock the chin. A recessed part 12 which is recessed with an inclined surface 12a from both sides is formed in the center in the direction of the short side.