The invention provides an ablation catheter capable of improving operability by extremely reducing anisotropy of torque transmitting performance depending on rotational direction while maintaining flexibility. An ablation catheter includes a shaft body (60) extending in an axial direction (X) with a spiral slit (61) formed at least partially thereto, and an electrode tip (31) arranged at the distal end part of the shaft body (60) which can be inserted into a living body to thermally influence biological tissue, wherein the shaft body (60) comprising a portion having different spiral inclination angles (±) which is an angle of the extending direction of the spiral of the slit (61) against the cross section orthogonal to the axial direction (X), while step parts (102) where the angle of the slit to the spiral inclination angle (±) changes locally are formed on one of the opposing surfaces (100) comprising the slit (61), and contacting parts (112) with which the step parts (102) contact when the shaft body (60) is twisted to the direction to unwind the spiral of the slit (61) are formed on the other opposing surface (110), while the length (L3) of the step parts (102) in the axial direction (X) is formed to be longer in the portion where the spiral inclination angle (±) is relatively large than in the portion where the spiral inclination angle is small.
