Provided is a medical elongated body that, while maintaining flexibility, suppresses anisotropy in the torque transmission performance resulting from rotational direction as much as possible, thus increasing operability. The medical elongated body has a base-end shaft (60) extending in the axial center direction (X) and to at least a portion of which a helical slit (61) is formed. The base-end shaft (60) is provided with a site at which the helical inclination angle (α), which is the angle in the direction of extension of the helix of the slit (61) with respect to a cross section that is perpendicular to the axial center direction (X), differs. A step section (102) at which the angle of the slit (61) with respect to the helical inclination angle (α) locally changes is formed at one opposing surface (100) configuring the slit (61), a contact section (112) that the step section (102) contacts when the base-end shaft (60) is twisted in the direction loosening the helix of the slit (61) is formed at the other opposing surface (110), and the length (L3) in the axial center direction (X) of the step section (102) is formed longer at a site at which the helical inclination angle (α) is relatively large than a site at which same is small.L'invention concerne un corps allongé médical qui, tout en conservant de la souplesse, supprime autant que possible l'anisotropie dans la performance de transmission de couple résultant du sens de rotation, ce qui augmente l'efficacité opérationnelle. Le corps allongé médical présente une tige (60) à extrémité de base, s'étendant dans la direction centrale axiale (X) et dont au moins une partie présente une fente hélicoïdale (61). La tige (60) à extrémité de base comporte un site qui présente un angle d'inclinaison hélicoïdale (α) différent qui est l'angle de la direction d'extension de la structure hélicoïdale de la fente (61) par rapport à une section transversale perpendiculaire à la direction centrale axiale (X). Une section à gradin (1
