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 (α), 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 (α) 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 (α) is relatively large is formed to be longer than that in a site in which the spiral inclination angle (α) is relatively small.
