Indwelling needle assembly

An indwelling needle assembly comprising a stylet having a sharp needlepoint at its end, a stylet hub secured to the base end part of the stylet, a hollow outer needle in which the stylet is inserted, an outer needle hub secured to the base end part of the outer needle, an opening so formed at the base end part or the side part of the outer needle hub as to communicate with the inner cavity of the outer needle, a seal member which is fitted to the outer needle hub and in which a hole or a slit for inserting the stylet therein is so formed as to be closed when the inserted stylet is extracted, an operation part installed on the outer needle hub for operating movement of the stylet and the outer needle along the longitudinal direction while the stylet is inserted into the outer needle, and a movement suppressing means for stopping or suppressing the movement of the stylet relative to the seal member when the operation part is operated.