To improve the quality of an end face by preventing a space part from generating by preventing a discontinuous part from generating on a roller end part.

In forming a brush on the end face of the end part by blocking the roller end part in which the brush is provided on the outer periphery of a resin made cylindrical core tube, a heating process S1 in which one end part of a core tube is heated with a heater, a throttling process S2 in which the heated one end part of the core tube is pressured by a pressurizer from the outer periphery of the one end part to an axis side of the core tube, and the opening of the one end part is throttled and a throttle is formed, and an indentation process S3 in which a push rod is brought into press contact with the throttle and moved along the axis, and the throttle is pushed inside the core tube and closed are provided.