To make a mattress of first dimension standard and a mattress of a second dimension standard mutually convertible, to make it easy to convert, to make conversion easy, and to reduce costs of conversion in a mattress having a plurality of dimension standards.SOLUTION: A mattress of a rectangular parallelepiped shape can mutually convert a first mattress 1 of first dimension standard and a second mattress 2 that has second dimension standard set larger than the first dimension standard and shares thickness. The first mattress 1 and the second mattress 2 have a width direction X, a lengthwise direction Y, and a thickness direction Z. A width direction additional member 3 has a rectangular parallelepiped shape which cannot be connected or separated in the width direction X at an end part in the width direction X of the first mattress 1, and an epidermis 1c of a top surface of an epidermis 1b of the first mattress 1 has a pair of width extension parts 1d outside in the width direction X, has a first connection member 4 on a back surface of the width extension part 1d and a top surface of the width direction additional member 3, and has a second connection member 5 at an end part in the width direction X of the first mattress 1 and on a side surface in the lengthwise direction Y of the width direction additional member 3.SELECTED DRAWING: Figure 1【課題】複数寸法規格を有するマットレスにおいて、第１寸法規格のマットレスと第２寸法規格のマットレスを相互に変換可能にすること、変換が容易であること、変換のコストを低減すること。【解決手段】マットレスは、第１寸法規格の第１マットレス１と、第１寸法規格よりも大きく設定され、厚さが共通の第２寸法規格を有する第２マットレス２と、を相互に変換可能な直方体形状のマットレスであり、第１マットレス１及び第２マットレス２が幅方向Ｘ、長さ方向Ｙ及び厚み方向Ｚを有し、幅方向付加部材３は第１マットレス１の幅方向Ｘの端部に幅方向Ｘに連結及び分離が可能な直方体形状であり、第１マットレス１の表皮１ｂのうちの天面の表皮１ｃが幅方向Ｘの外側に一対の幅延長部１ｄを有し、幅延長部１ｄの裏面及び幅方向付加部材３の天面に第１連結部材４を有し、第１マットレス１の幅方向Ｘの端部及び幅方向付加部材３の長さ方向Ｙの側面に第２連結部材５を有する。【選択図】 図１
