It is an object of the present invention to provide a balloon-type ablation catheter that can measure the electric potential around the entire circumference of the pulmonary vein at a position near the left atrium with electrodes attached to a catheter distal end part of an electrode catheter inserted in a shaft in a state where a balloon is pressed against the area around the ostium of the pulmonary vein. The balloon-type ablation catheter of the present invention includes a catheter shaft (10) having a multi-lumen structure in which a plurality of lumens (11 to 17) are formed that include a liquid feeding lumen (13), (16) and an electrode catheter insertion lumen (12), a distal end tip (30) attached to the distal end of the catheter shaft (10), a balloon (50) attached to the distal end part of the catheter shaft (10), and a high-frequency current application electrode (70) provided in the balloon (50). A side hole (32) that communicates with the electrode catheter insertion lumen (12) and that opens on the side peripheral surface of the distal end tip (30) is formed in the distal end tip (30).
