An indwelling needle assembly usable in combination with an infusion system for infusion into a patient s body is disclosed. The indwelling needle assembly is comprised of a needle having a needlepoint insertable into the patients body a sleeve slidably fitted on the needle a catheter including a catheter tube slidably fitted on the sleeve a base body fixed to a proximal end of the needle and a slider fixed to the sleeve and slidably engaged with the base body so as to be movable between a first position to have the needlepoint projecting out of the sleeve and a second position to have the needlepoint retracted in the sleeve, wherein the needle, the sleeve, the base body and the slider are unitarily extractable from the catheter.
