To provide a method for manufacturing an interdental cleaning tool that can prevent deformation of a core base at molding of a cleaning flexible part using an elastomer material, thereby effectively preventing occurrence of molding failure of the cleaning flexible part. The method in the present invention includes: a base part molding step of providing first metal molds 30 and 31 for molding base parts with a plurality of first molding spaces 32 aligned in parallel and including core base molding sections 32a and handle base molding sections 32b, providing the first metal molds 30 and 31 with connection part molding sections 35 to communicate with the adjacent handle base molding sections 32b, and supplying a synthetic resin material with a fiber material at a time to the plurality of first molding spaces 32 from gates 34 to form a plurality of base parts at a time; and a flexible part molding step of setting the core bases of the base parts into second metal molds, holding the core bases at two or more longitudinal portions by a plurality of pairs of hold pins in the second metal molds, each pair including two pins, and charging an elastomer material into the cleaning flexible part molding spaces.