The present invention relates to a method for separating and washing microparticles via a stratified co-flow of non-Newtonian fluid and Newtonian fluid, wherein the Newtonian fluid as well as the non-Newtonian fluid may flow into a transfer channel formed in a fluid chip at a predetermined flow rate ratio matching with an effective diameter of the target particles contained in the non-Newtonian fluid, thereby inducing a change in positions of particle focusing points with respect to the target particles within the stratified co-flow thereof formed in the transfer channel. As a result, it is possible to more easily separate only the target particles among the microparticles contained in the non-Newtonian fluid toward the Newtonian fluid without using an additional device and human power, or transfer the target particles contained in the non-Newtonian fluid toward the Newtonian fluid for washing the same. Accordingly, since native biofluids used in the studies and clinical experiments are mostly non-Newtonian fluid, it is possible to directly separate and wash the target particles without a need of changing a solution for containing cells/particles or additional diluting the same for executing experiments. If the native biofluids as the non-Newtonian fluid lack a relaxation time, any artificial polymer could be simply added thereto in order to increase the relaxation time, thereby greatly increasing an amount of treatment per time. Further, since high working efficiency can be achieved in a wide range of flow rate, high efficient separation and washing processes may be achieved by a simple hand work of pushing and pumping an injector alone, without any accurate pumping device.