Aiming to provide a method capable of reciprocatingly delivering various liquids without bringing air into a microchannel, a detection system and a detection apparatus for implementation of this method. In order to achieve at least one of the above aims, provided is a method of inserting a pipette tip into a liquid injection portion of a detection chip including: the microchannel; the liquid injection portion connected to one end of the microchannel; and a reservoir connected to the other end of the microchannel, injecting and aspirating the liquid by the pipette tip, and reciprocatingly delivering the liquid into the microchannel. At this time, the following steps are executed in this order, the steps including: inserting the pipette tip into the liquid injection portion up to a position at which an end of the pipette tip comes below a liquid level when the liquid is injected into the liquid injection portion; injecting the liquid from the pipette tip into the liquid injection portion; generating a negative pressure in the liquid injection portion to raise the level of the liquid in the liquid injection portion; and performing either aspiration of the liquid in the liquid injection portion by the pipette tip, or injection of the liquid into the liquid injection portion by the pipette tip and aspiration of the liquid inside the liquid injection portion.