PROBLEM TO BE SOLVED: To provide an ablation catheter, and a method for electrically insulating (segregating, separating, shutting off and isolating) cardiac tissue.SOLUTION: An ablation catheter 1 includes a slender member having a proximal end and a distal end 21. The distal end is configured to apply a high-energy electric shock from a plurality of positions along a lengthwise direction of the distal end. The distal end is curved. Preferably, the distal end of the slender member is extended like a circular segment.