An anti-blocking agent master batch is provided, obtained by compounding 100 parts by mass of a polyolefin-based resin with 1 to 40 parts by mass of polymer fine particles, the polymer fine particles obtained by: causing two or more fluids including a liquid medium, a monomer or monomers, and a polymerization initiator to continuously and successively pass through a plurality of net bodies which are disposed at given intervals in a cylindrical passage and each have a surface crossing a direction of the passage to obtain an emulsion including liquid droplets containing the monomer or monomers and the polymerization initiator, the liquid droplets being dispersed in the liquid medium; and heating this emulsion to polymerize the monomer or monomers. Also provided is a manufacturing method thereof. The anti-blocking agent master batch can prevent the generation of die build-up during the manufacture of a master batch for a polyolefin-based resin film by compounding an anti-blocking agent into a polyolefin-based resin.