To provide a mattress capable of not only obtaining an excellent sleeping feeling but also being freely bent corresponding to a reclining bed.

A mattress main body 11 formed in a thick plate shape by filling air is provided with an upper surface sheet 12 and a lower surface sheet 13 facing each other, and the sheets 12 and 13 are connected through many connecting threads 15. A pair of partition films 16 and 17 are provided in parallel inside the mattress main body 11, and a bend chamber 18 is sectioned by the partition walls 16 and 17. When raising the back plate 33 of the reclining bed 32, by discharging air from the bend chamber 18 and lowering the rigidity of the respective sheets sectioning the bend chamber 18, it becomes possible to bend the mattress main body 11 along the bend chamber 18. Also, since it is bent by the pressure reduction of the bend chamber 18, recessed and projected parts are not formed on the surface of the mattress, and a pressure applied to the body is dispersed.