A separator includes: a channel having a first surface; a plurality of columnar members formed on the first surface and having a cross section in the shape of a crescent, the plurality of columnar members being arranged in a row direction along a longitudinal direction of the channel, and in a column direction perpendicular to the longitudinal direction of the channel, the columnar members that belong to the same row from among the plurality of columnar members being disposed so that the crescents face the same direction in the column direction, the columnar members that belong to a single row being disposed so that the crescents face the opposite direction in the column direction with respect to the crescents of the columnar members that belong to the adjacent row; and a substance that specifically binds to a separation target, and is disposed on side surfaces of the plurality of columnar members.