Provided is an ablation catheter that, while securing flexibility, suppresses anisotropy of torque transmission performance resulting from rotational direction as much as possible, and thus is able to increase operability. The ablation catheter (10) has: a shaft main body (60) extending in the axial center direction (X) and at which a helical slit (61) is formed and an electrode chip (31) that imparts a thermal influence on in vivo tissue and that is provided to the tip end, which can be inserted into a living body, of the shaft main body (60). The shaft main body (60) is provided with a site at which there is a different helical inclination angle (α), which is the angle of the direction of extension of the helix of the slit (61) with respect to a cross section perpendicular to the axial center direction (X). 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 shaft main body (60) is twisted in the direction of 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 the site at which the helical inclination angle (α) is relatively large than at a small site.Linvention concerne un cathéter dablation qui, tout en garantissant de la souplesse, supprime autant que possible lanisotropie de la performance de transmission de couple résultant du sens de rotation, ce qui permet daugmenter lopérabilité. Ledit cathéter dablation (10) présente : un corps principal (60) de tige sétendant dans la direction centrale axiale (X) et au niveau duquel est ménagée une fente hélicoïdale (61), et une puce délectrode (31) qui exerce une influence thermique sur des tissus in vivo et est disposée à lextrémité de la pointe du corps principal (60) de la tige, qui
