Disclosed is a method for separating immunomagnetic bead labeled particulates. A carrier board is formed with at least one flow channel structure, which includes an inner reservoir, an outer reservoir, and at least one micro flow channel in communication with the inner reservoir and the outer reservoir. The method includes labeling target particulates with immunomagnetic bead, introducing a sample fluid into the inner reservoir, and applying a magnetic force and a driving force, wherein the driving force drives the particulates not labeled with immunomagnetic bead to flow through the micro flow channel to the outer reservoir, while the magnetic force attracts the particulates labeled with the immunomagnetic bead to retain in the inner reservoir. The driving force may be centrifugal force, pressure, or surface tension.