Abstract: A medical device includes a liquid circulation unit that enables transfer of a liquid (a perfusion liquid) supplied from a port unit of a second hub of an energy application device to a distal end portion of a first shaft of a catheter device. The energy application device is relatively movable forward and backward with respect to the catheter device so that an energy application unit can be disposed at a predetermined position on the distal end side of the first shaft.

Abstract: At a distal portion of a shaft of a guide portion included in a medical device, a first portion is configured to be capable of coming into contact with an inner wall of a living organ. A second portion is disposed on a proximal side of the shaft with respect to the first portion. The second position is configured to be capable of coming into contact with the inner wall of the living organ at a position different from that of the first portion on a transverse cross section of the inner wall of the living organ. A treatment portion is movable in a lumen of the shaft in a state where at least a part of the first portion and at least a part of the second portion come into contact with the inner wall of the living organ.