Abstract: Plural types of cells having different dielectrophoretic properties are separated using a simple structure. There is provided a cell separation device including: a flow path through which a cell suspension flows, the cell suspension containing plural types of cells which have different dielectrophoretic properties; electrodes disposed to face each other in a direction intersecting a flow direction of the cell suspension flowing in the flow path; an electric field gradient forming portion which generates an electric field strength gradient between the electrodes; and a power supply applying an alternating voltage having a direct current component across the electrodes.