An objective of the present invention is to provide an indwelling needle assembly that has a novel structure and improves operability for the practitioner. An indwelling needle assembly 10 in which an inner needle unit 16 comprises a storage housing 14 for storing a protector 52, and which is provided with a connecting member 94 that connects the storage housing 14 to an outer needle hub 20. The protector 52 prevents movement of the connecting member 94 and holds the storage housing 14 and the outer needle hub 20 in a connected state. Deformation or displacement of the protector 52 due to retraction of an inner needle 12 permits the movement of the connecting member 94 and makes it possible to release the connected state between the storage housing 14 and the outer needle hub 20.