A radiofrequency electric current ablation catheter comprising a tip electrode, a means for detecting temperature of the tip electrode, a catheter shaft and a portion for operation at proximal end, wherein the tip electrode has a shape formed by connecting three or more spherical or approximately spherical surfaces having centers on the same straight line to each other with a curved surface. The tape reel includes a plurality of arc-shaped convex parts that are disposed on a circle about an axis of the hub on the inner surface of the base plate and support the locking member that has moved toward the base plate. The construction is further provided with own propulsion means, which results in a wide range of application possibilities and a high degree of flexibility in use.