An ablation catheter system with a balloon, comprising: an ablation catheter with a balloon comprising: a catheter shaft; a balloon fixed to a front side in a longitudinal direction of the catheter shaft; a lumen communicating with the balloon from an end section on a rear side in the longitudinal direction; an in-balloon electrode and an in-balloon temperature sensor arranged in an interior of the balloon; and a front portion electrode and a front portion temperature sensor attached to a front area containing an end section on the front side in the longitudinal direction, wherein a distance from the end section on the front side in the longitudinal direction of the catheter shaft to a front end of the front portion electrode in the longitudinal direction is 4 to 10 mm; and a circuit switching switch configured to switch between a first balloon heating circuit (a) and a front end heating circuit (b): (a) the first balloon heating circuit having the in-balloon electrode, a counter electrode, the in-balloon temperature sensor, and a radio-frequency generator, (b) the front end heating circuit having the front portion electrode, the counter electrode, the front portion temperature sensor, and the radio-frequency generator. an ablation catheter with a balloon comprising: a catheter shaft; a balloon fixed to a front side in a longitudinal direction of the catheter shaft; a lumen communicating with the balloon from an end section on a rear side in the longitudinal direction; an in-balloon electrode and an in-balloon temperature sensor arranged in an interior of the balloon; and a front portion electrode and a front portion temperature sensor attached to a front area containing an end section on the front side in the longitudinal direction, wherein a distance from the end section on the front side in the longitudinal direction of the catheter shaft to a front end of the front portion electrode in the longitudinal direction is 4 to 10 mm; and a catheter shaft; a balloon fixed to a front side in a longitudinal direction of the catheter shaft; a lumen communicating with the balloon from an end section on a rear side in the longitudinal direction; an in-balloon electrode and an in-balloon temperature sensor arranged in an interior of the balloon; and a front portion electrode and a front portion temperature sensor attached to a front area containing an end section on the front side in the longitudinal direction, wherein a distance from the end section on the front side in the longitudinal direction of the catheter shaft to a front end of the front portion electrode in the longitudinal direction is 4 to 10 mm; and a circuit switching switch configured to switch between a first balloon heating circuit (a) and a front end heating circuit (b): (a) the first balloon heating circuit having the in-balloon electrode, a counter electrode, the in-balloon temperature sensor, and a radio-frequency generator, (b) the front end heating circuit having the front portion electrode, the counter electrode, the front portion temperature sensor, and the radio-frequency generator. (a) the first balloon heating circuit having the in-balloon electrode, a counter electrode, the in-balloon temperature sensor, and a radio-frequency generator, (b) the front end heating circuit having the front portion electrode, the counter electrode, the front portion temperature sensor, and the radio-frequency generator.