To provide a mat which can eliminate backache, numbness in a limb or the like and can be mass-produced with inexpensive facilities.

Unilateral mat bodies 1A, 1A are connected together with outer hinge members 5, 5 and internal hinge members 7, 7 so that they can be folded in a direction or only to the back side. Then, a mat body 1 which is connected so that it can be folded only to the back side is covered with a cover 8. The mat body 1 which has the connected unilateral mat bodies 1A, 1A is contained in and covered with the cover 8 so that the face which is not formed with Velcro fasteners 9 can contact the lower back or the like of a sleeper and the face formed with the Velcro fasteners 9 can be on the folded side of the mat body 1.