A cell separation container includes a collection chamber and a tissue holding chamber which are partitioned by a filter. The cell separation container includes a first air pressure adjuster configured to adjust the inflow and outflow of gas in the collection chamber and a second air pressure adjuster configured to adjust the inflow and outflow of gas in the tissue holding chamber. Thus, the inflow and outflow of the outside air and the gases in the collection chamber and the tissue holding chamber can be adjusted. In the cell separation container, switching between holding a treatment liquid in the tissue holding chamber and ejecting a treatment liquid to the collection chamber can be performed by adjusting the inflow and outflow of the outside air and the gas in the connection chamber.