PROBLEM TO BE SOLVED: To provide a catheter unit which can automatically follow variations of blood vessel diameters due to individual differences.SOLUTION: A catheter unit 1 includes a plurality of basket filters 5 which can capture thrombi in blood vessels, and is inserted into a target region inside a body of a patient or is removed from the target region to the outside of the body of the patient. The catheter unit is equipped with an outer cylindrical master catheter 2, an inner cylindrical slave catheter 3 which is slidably inserted in the master catheter, and a pusher catheter 4 which can position a tip end of a distal side of the slave catheter 3 at a desired position relative to a tip end of a distal side of the master catheter 2 by pressing the slave catheter 3 inserted in the master catheter 2 to a distal side. The basket filters 5 have a proximal side firmly fixed on the distal side of the master catheter 2 and a distal side firmly fixed on the slave catheter 3, and are configured to be able to automatically enlarge or reduce the diameter in the form of a basket in accordance with variations of blood vessel diameters in the target region.
