To smoothly fit a double folded part of a brush single body nipping a core to a fitting groove of a rotating shaft, in a brush.

The fitting grooves 12 having narrow opening portions 13 and extending in the axial direction are arranged in a plurality of positions in the circumferential direction of the outer periphery of the rotating shaft 11. At least one end of the fitting grooves 12 along the axial direction is opened to the end face of the rotating shaft 11, and the core 22 is nipped in the double folded portion 21A of the brush single body 21. The double folded portion 21A of the brush single body 21 and the core 22 are fitted to the fitting groove 12 from one end of the each fitting groove 12 opened to the end face of the rotating shaft 11. A nipping tool 23 is adhered around the double folded portion 21A of the brush single body 21 nipping the core 22, and the double folded portion 21A of the brush single body 21 and the nipping tool 23 are fitted to the fitting groove 12 of the rotating shaft 11.