The invention provides a medical elongated body which can improve the operability by suppressing anisotropy of torque transmission performance in accordance with the rotational direction as much as possible while maintaining flexibility. Provided is a medical elongated body having a proximal shaft (60) which extends in an axial center direction (X) and includes at least a part of which a spiral slit (61) is formed. The proximal shaft (60) includes a site in which the spiral inclination angles (±), which are angles in an extending direction of a spiral of the slit (61) with respect to a cross-section orthogonal to the axial center direction (X), are different from each other, and a stepped portion (102) in which the angle of the slit (61) changes locally with respect to the spiral inclination angle (±) is formed on one opposed surface (100) constituting the slit (61), and an abutting portion (112) on which the stepped portion (102) abuts when the proximal shaft (60) is twisted in a direction in which the spiral of the slit (61) is released is formed on the other opposed surface (110). A length (L3) of stepped portions (102) in the axial center direction (X) in a site in which the spiral inclination angle (±) is relatively large is formed to be longer than that in a site in which the spiral inclination angle (±) is relatively small.
