Provided is a high frequency balloon catheter system which has a balloon (6) that can be freely deflated by suction of a balloon internal fluid without significantly changing the profile of the balloon (6) and allows the system to easily pass through narrow regions, and which when a coolant is injected inside the balloon (6), discharges the coolant outside along with the expansion of the balloon (6) and cools the balloon (6), and heats and expands the narrow region while protecting an internal membrane. A catheter shaft (1) is configured from an inner cylindrical shaft (3) and an outer cylindrical shaft (2) which are slidable on one another. The collapsible and expandable balloon is disposed between a tip end (5) of the inner cylindrical shaft (3) and a tip end (4) of the outer cylindrical shaft (2). A front neck (6A) of the balloon (6) covers the inner cylindrical shaft (3) with the front neck (6A) and the inner cylindrical shaft (3) being in proximity to each other to form a check valve (8). More specifically, sucking the internal fluid of the balloon (6) to establish negative pressure therein causes the check valve (8) to close and the balloon (6) to deflate, and injecting the internal fluid to establish positive pressure therein causes the balloon (6) to expand and the check valve (8) to open such that the internal fluid is discharged outside. A high frequency current carrying electrode (11) is also disposed inside the balloon (6), said high frequency current carrying electrode (11) being connected to a high frequency generator (41) by a current carrying wire (42) inside the catheter shaft (1). An infusion pump (29) which delivers a cooling water (C) is connected to a fluid delivery path (9) which is in continuous communication with the inside of the balloon (6).Linvention concerne un système de cathéter à ballonnet haute fréquence qui comporte un ballonnet (6) qui peut être librement dégonflé par aspiration dun fluide interne de ballonnet sans modifier de façon
