Mononuclear cell separation column, mononuclear cell separation system, method for separating out mononuclear cells, mononuclear cells, and drug for internal administration

Provided is a mononuclear cell separation column that is for mononuclear cells and that is capable of separating out mononuclear cells in a simple manner. The mononuclear cell separation column is provided with: an upper chamber (110) in which a sample solution is held before centrifugal separation processing and in which mononuclear cells, which are a low density component, are positioned after centrifugal separation processing; a lower chamber (120) in which a centrifugal separation medium is held before centrifugal separation processing and in which high density components, which are unneeded components, are positioned after centrifugal separation processing; a three-way stopcock (130) that openably/closably connects the bottom aperture of the upper chamber (110) and the upper aperture of the lower chamber (120); and a lid (140) that plugs the upper aperture of the upper chamber (110).