A catheter assembly (10) comprises an inner needle (12), a catheter (14), and a needle cover (40). The needle cover (40) includes an inner tube (70) and an outer tube (80) which moves relative to the inner tube (70) when the inner needle (12) is removed. The inner tube (70) has a stopper portion (100) integrally formed therewith which prevents the inner tube (70) and the outer tube (80) from separating by being disposed in a standby position radially outboard of the inner tube (70) when the inner needle (12) is inserted through the catheter (14). The stopper portion (100) is disposed in an inner needle blocking position opposing the tip of the inner needle (12) by sliding with the relative movement of the outer tube (80).
