PROBLEM TO BE SOLVED: To provide a backrest of a chair that can narrow a gap of left and right sacroiliac joints where the ligament is relaxed to be spread and displaced, regardless of a pelvic size, and thereby can correct it in a normal position.SOLUTION: A backrest of a chair includes the backrest capable of coming in abutment with a region falling under the pelvis of a seated person. The backrest of the chair is characterized in that the backrest includes a right backrest part and a left backrest part. In the horizontal direction, and when the inside in each of the left and right directions of the right backrest part and the left backrest part is pressed to the rear direction by a region applicable on the periphery of a sacrum of the pelvis in a plan view, and rotated or twisted, the outside in each of the left and right directions of the right backrest part and left backrest part is rotated or twisted in the direction for pressing the region applicable on the rear outside of the hip-bone of the pelvis toward the sacrum side by the rotation or twist.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2019,JPO&INPIT【課題】骨盤の大きさにかかわらず、靱帯が弛緩して広がりずれた左右の仙腸関節の隙間を狭くし正常な位置に矯正できる椅子の背凭れを提供することを課題とする。【解決手段】着座者の骨盤に該当する部位に当接可能な背凭れを備える椅子の背凭れであって、前記背凭れは左右方向で右背凭れ部と左背凭れ部を備え、平面視で、前記右背凭れ部と左背凭れ部のそれぞれの左右方向での内側が骨盤の仙骨周辺に該当する部位により後方向に押圧され回転又は捩れたときに、前記回転又は捩じれにより、前記右背凭れ部と左背凭れ部のそれぞれの左右方向での外側が骨盤の寛骨の後部外側に該当する部位を仙骨側に向けて押圧をかける方向に回転又は捩れることを特徴とする椅子の背凭れにより課題解決できた。【選択図】 図１
