The present invention relates to a girder back support for a chair in which a girder back, which is vertical with respect to the horizontal axis at the rear of a seat board of the chair and supports the spine, is formed to support and correspond to the vertebrae only. Provided is a girder back support for a chair, which is mounted at the rear of a seat board of the chair and used as a backrest, the girder back support comprising: a spine girder which is vertically formed on the center line of the horizontal axis and has a front surface forming a curved surface along the curved shape of the spine a pair of transverse girders which are vertically formed on the left and right sides of the spine girder to be symmetrically spaced apart at a predetermined distance and have a front surface forming a curved surface along the curved shape of both sides of the spine a fixing and connecting part for fixing the spine girder and the pair of the transverse girders to be spaced apart from each other and a coupling part formed at the lower end of the back side of the spine girder and the pair of the transverse girders.La présente invention concerne un support de montant dorsal pour une chaise, dans lequel un montant dorsal, qui est vertical par rapport à laxe horizontal à larrière dune plaque de siège de la chaise et supporte la colonne vertébrale, est formé pour soutenir et correspondre aux vertèbres uniquement. Linvention concerne un support de montant dorsal pour une chaise, qui est monté à larrière dune plaque de siège de la chaise et utilisé comme dossier, le support de montant dorsal comprenant : un montant de colonne vertébrale qui est formé verticalement sur la ligne centrale de laxe horizontal et a une surface avant formant une surface incurvée le long de la forme incurvée de la colonne vertébrale une paire de montants transversaux qui sont formés verticalement sur les côtés gauche et droit du montant de colonne vertébrale pour être espacés de manière symétrique dune dist
