To provide a particle removing apparatus for removing plankton included in seawater to be used as ballast water by a method other than membrane separation.

The particle removing apparatus 10 for the ballast water for solving the problem is provided with a main flow path 12 through which brought seawater therein is made to flow and a branch flow path 14 through which a flow branched from the main flow path 12 is made to flow, the main flow path 12 is constituted such that it is repeatedly contracted and expanded, disturbance is generated in fluid flowing through an expansion part 12b, the fluid introducing port 13 of the branch flow path 14 is formed at the expansion part 12b of the main flow path 12, and a difference is provided in the ratio of the amount of particles included in the seawater flowing through the main flow path 12 and the amount of the particles included in the seawater flowing through the branch flow path 14. Additionally, in the particle removing apparatus 10 of such constitution, it is desirable to form the fluid introducing port 13 of the branch flow path 14 narrower than the particle size of the particles desired to be removed.