The invention mainly discloses a manufacturing method of granular iron oxide black pigment, which comprises the steps of: sending iron black block material with the water content of 1-2% into a double-roller grinder, and grinding the dry iron black block material into granules with the needed size in the double-roller grinder; then, classifying by a rotary vibration sieve; and collecting granulariron oxide black of 20-80 meshes. The technique has the advantages of solving the problem of the occupational disease caused by dust pollution of iron oxide pigment industry, improving the working environment of workers and protecting the health of the workers. The invention also discloses the double-roller grinder for realizing the method, the upper part of the grinder is provided with a pair ofrollers which are provided with a fit clearance adjusting mechanism; three layers of vibrating screens which are driven by an eccentric motor and have the number of sieve meshes that are increased gradually from top to bottom are positioned just under the rollers; and the edges of the vibrating screens are provided with discharge holes. The double-roller grinder leads the material to be bitten into a grinding area by utilizing the frictional force of roller surfaces, thus crushing the material by extruding or splitting.