PROBLEM TO BE SOLVED: To provide a bathtub which enables a bather to relax by materializing a posture in which the spinal standing muscle group is relieved.SOLUTION: There are configured to inwardly form a recess, with a vertically continuously bent concave surface, a headrest part 21 which supports the head by projecting upward against the inner wall face 11 of a bathtub 1, a back holding part 22 which supports an area from the back to the waist, and a hip holding part 23 which holds the hip. As the back holding part 22, there are formed line-symmetrically and in a shape of V cross-sectionally, a relief recess 221 that extends vertically in a manner relieving the spinous processes of the spine of a bather, holding surface parts 222, 222 that, in both side positions in the width direction, hold in surface contact the back part on both sides sandwiching the spine of the bather, and the slope parts 223, 223 that, in both outer side positions, expands in a manner directing the bust of the bather toward the center line X side.COPYRIGHT: (C)2014,JPO&INPIT【課題】 脊柱起立筋群を緩めた状態の姿勢を実現させて入浴者をリラックスさせ得る浴槽を提供することにある。【解決手段】 浴槽1の内壁面11に対し、上側に突出して頭部を支持するヘッドレスト部21と、背中から腰部を支持する背中保持部22と、臀部を保持する臀部保持部23とを、内向きに凹となるように上下方向に連続して湾曲する凹曲面によって構成する。背中保持部22として、入浴者の脊柱の棘突起を逃がすよう上下方向に延びる逃がし凹部221と、幅方向両側位置で入浴者の脊柱を挟む両側の背中部分と面接触して保持する支持面部222,222と、両外側位置において入浴者の上半身を中心線X側に向かわせるように拡がる斜面部223,223とを、線対称でかつVの字状の横断面形状に形成する。【選択図】 図1
