The purpose of this invention is to provide a balloon catheter whereby rupture of the balloon due to liquid being forced into the balloon with the balloon extended or treatment with a balloon shape that is unsuitable for treatment can be prevented. This invention provides a balloon catheter that comprises the following: an inside-tube shaft that has a narrow inside-tube section at the distal end and a wide inside-tube section at the proximal end； an outside-tube shaft with the inside-tube shaft inserted into the lumen thereof； a balloon, the distal end of which is affixed to the distal end of the inside-tube shaft and the proximal end of which is affixed to the distal end of the outside-tube shaft, that changes between a normal shape and an extended shape as a result of the outside-tube shaft and the inside-tube shaft sliding against each other； and a housing that connects to the lumen of the outside-tube shaft and has a narrow lumen at the distal end and a wide lumen at the proximal end. When the balloon is extended, the wide inside-tube section of the inside-tube shaft is inserted into the narrow lumen of the housing, blocking the insertion of liquid into the balloon.本發明之目的在於提供一種附有氣球的導管，該附有氣球的導管可防止因於氣球伸張形狀時勉強通液所致氣球之破裂及以不適於治療的氣球形狀進行治療之情況。本發明提供一種附有氣球的導管，該附有氣球的導管具備：內筒軸，其前端側具有小徑的內筒部，且基端側具有大徑的內筒部；外筒軸，其內腔被前述內筒軸插入；氣球，其前端固定於前述內筒軸的前端，且基端固定於前述外筒軸的前端，藉由前述外筒軸與前述內筒軸相互地滑動而在氣球平常形狀與氣球伸張形狀之間變化形狀；及外殼，其連通前述外筒軸的內腔，且於前端側具有小徑的內腔及於基端側具有大徑的內腔，前述外殼係具有插入前述內筒軸的插入口，以及使液體在前述氣球及前述外筒軸流出/流入之液體流出/流入口。
