A indwelling needle includes an outer needle, an outer needle hub which has a flow path communicating with the inside of the outer needle and can connect a connector to the flow path, and a valve mechanism which opens and closes the flow path. The valve mechanism is provided with a valve element which is provided in the middle of the flow path and has an opening/closing section, which can be opened and closed, consisting of an elastic material, and an operation member which has a side hole and operates the opening and closing of the opening/closing section. The valve mechanism can have a state in which the operation member penetrates through the opening/closing section so as to protrude therefrom and in which the side hole is located closer to the front end side than the opening/closing section. When an infusion liquid is supplied in this state from the connector, the infusion liquid flows out to the flow path through the side hole and the dead space within the flow path is filled with the infusion liquid having flowed out through the side hole.
