To surely implant brush fibers in an adhesive layer by preparing brush fibers to have a sharp angle part on at least one end of each fiber of both ends where the brush fiber is to be implanted in an adhesive layer.

A developing roller 2 consists of a core body 5 which can freely rotate, an adhesive layer 6 and a developing brush 8 of brush fibers 7. As for the developing brush 8, resin fibers such as nylon, rayon and acryl or conductive fibers can be used. Both ends of each brush fiber 7 which constitutes the developing brush are cut oblique to the longitudinal direction of the brush fiber to make a sharp angle 7A at the top end. When the brush fiber 7 thus prepared is made to fly to the adhesive layer 6, the fiber sticks on the surface of the adhesive layer 6 and implantation of brush fibers 7 can be completed in a short time. Even when an adhesive layer having high viscosity with addition of carbon is used, electrostatic implantation can be surely performed.