A balloon ablation catheter achieves reduction in diameter of the balloon upon balloon contraction and increased reliability of the thermocouple temperature sensor, which balloon ablation catheter is less likely to be influenced by the heating liquid discharged into the balloon and able to control the balloon surface temperature with high accuracy. The balloon ablation catheter includes a shaft wherein a lumen is formed a balloon wherein the lumen communicates with the inside thereof and a high-frequency-current-applying electrode formed by coiling a high-frequency-power-supplying lead wire around the shaft while sandwiching a temperature sensor lead wire between the high-frequency-power-supplying lead wire and the shaft such that the temperature sensor lead wire is fixed along the longitudinal direction of the shaft wherein a thermocouple thermosensor is formed at the point where the high-frequency-power-supplying lead wire and the temperature sensor lead wire constituting the high-frequency-current-applying electrode contact with each other for the first time as seen from the posterior end side in the longitudinal direction.
