A catheter tube has a single-lumen distal-side tube and a single-lumen proximal-side tube, the distal-side tube and the proximal-side tube are connected in such a way that a lumen of the distal-side tube and a lumen of the proximal-side tube communicate with each other, a guide wire port that opens to the outside is provided in the distal-side tube, and the inner diameter of the lumen of the proximal-side tube is smaller than the inner diameter of the lumen of the distal-side tube,
