The present invention relates to a balloon catheter for treating elongate diseased vessels with a variable diameter, comprising a pre-stretched balloon (1) and a catheter shaft, which forms a wire lumen embodied to guide a guide wire and forms a liquid lumen by means of which a liquid can be fed to the balloon (1). The balloon (1) is fastened to a first catheter shaft element (5, 5) at a first, proximal fastening site (3) and fastened to a second catheter shaft element (4, 12) at a second, distal fastening site (2), wherein the second fastening site (2) is movable along a longitudinal axis of the catheter shaft in relation to the first fastening site (3). The balloon (1) surrounds a section of the catheter shaft which extends between the first and the second fastening site (3, 2). Here, the section of the catheter shaft surrounded by the balloon (1) encloses different regions of the catheter shaft with a changing longitudinal extent of the balloon (1).
