PROBLEM TO BE SOLVED: To further facilitate use of a catheter assembly by simplifying its operation at the time of use.SOLUTION: A catheter assembly 10 includes a catheter 12, a catheter hub 20 for holding the catheter 12, and an inner needle 14 that can be inserted into the inside of the catheter 12. Furthermore, the catheter assembly 10 includes an inner needle accommodation part 30 for holding the catheter hub 20 so as to be relatively movable, and accommodating the inner needle 14 inside by imparting acting force to retreat the inner needle 14 based on an advance of the catheter hub 20.
