Balloon catheter and balloon catheter system

A balloon catheter (15) comprising: a balloon (25); a catheter shaft (28) which comprises an outer tube shaft (30) connected to the proximal end of the balloon and an inner tube shaft (35) connected to the distal end of the balloon and in which the inner tube shaft passes through the outer tube shaft and the gap between the inner tube shaft and the outer tube shaft serves as a liquid passage (LP) communicated with the inner space of the balloon; a heating member (40) which is disposed on the outer peripheral surface of the inner tube shaft inside the balloon and which is for heating a liquid in the balloon; and a gap-retaining member (80) which is formed between the outer tube shaft and the inner tube shaft in such a manner that, in the connection part between the liquid passage and the inner space of the balloon, the outer peripheral surface of the inner tube shaft and the inner peripheral surface of the outer tube shaft are apart from each other throughout the peripheries of the outer peripheral surface and