A chip includes a micro-channel unit for hydraulically classifying cells in a blood sample. In a micro-channel unit, liquid flowing from a sub channel into a main channel pushes cells flowing in the main channel toward a side thereof on which a removal channel and a collection channel are disposed. Fluid containing non-nucleated RBCs among the pushed cells enters the removal channel, so that the non-nucleated RBCs are removed from a blood sample. A plurality of micro-channel units having the same patterns as each other are repeatedly stacked in a height direction. Inlets of the main channels, inlets of the sub channels, outlets of the removal channels, outlets of the collection channels, and outlets of the main channels, which are provided in the micro-channel units, are connected to respective pillar channels penetrating each of layers in a traversing manner.