A method of using a microsample treatment apparatus and an apparatus for detecting chemotaxis of cells and separating chemotactic cells includes a number of wells that are connected to each other via a part having resistance to fluids. The wells are each provided with tubes for injecting/sucking a sample and, if necessary, tubes for relieving pressure changes at the injection/suction. The tubes have a space in common at the top ends thereof in which a liquid can be held.