A balloon-type electrode catheter is capable of performing an ablation treatment with respect to a lesion over a wide area and excellent in an effect of cooling the inner portion of a balloon. The balloon-type electrode catheter includes an outer tube, an energization connector, a balloon having neck portions at both ends of an expansion portion, an inner tube, a distal end tip, strip electrodes formed on the outer surface of the balloon, and a conducting wire that connects each of the strip electrodes and the energization connector to each other. Openings of fluid supply sub lumens of the outer tube are located on the distal end side from an intermediate location in the axial direction in the expansion portion of the balloon. Openings of fluid drainage sub lumens of the outer tube are located at the proximal end of the expansion portion.