A method for setting a dielectric layer in a brushless motor including a rotor having the dielectric layer made of insulating resin, the brushless motor comprising: a stator including a stator iron core wound with a stator winding; the rotor disposed rotatably on a shaft, the rotor including a rotary body that holds a permanent magnet, and the shaft that extends through the center of the rotary body and joined to the rotary body; a bearing for supporting the shaft, the bearing including iron balls, an outer ring and an inner ring, and being provided with grease therein; and a conductive bracket for fixing the bearing, wherein the shaft is fixed to the inner ring of the bearing and the outer ring of the bearing is fixed by the bracket, the rotary body has the ferrite magnet at an outermost periphery of the rotary body, and an outer iron core of a rotor iron core, the dielectric layer, and an inner iron core of the rotor iron core are disposed in this order toward an inside, the dielectric layer is a layer made of the insulating resin, and has a ring shape and is disposed between an inside and an outside of the rotary body so that the dielectric layer orbits around the shaft, and the rotary body is joined to the shaft at a joint inside of the inner iron core, the method comprising: setting a rotor-body electrostatic capacity Cr that is an electrostatic capacity between the shaft and an outermost wall of the rotary body by adjusting at least a width in a radial direction and a material of the dielectric layer of the rotary body, the method being characterized in measuring a bearing electrostatic capacity Cb that is an electrostatic capacity between the inner ring and the outer ring when the bearing is rotated at 1000 r/min; and in that the dielectric layer is set to be so adjusted that the rotary-body electrostatic capacity Cr is set smaller than the bearing electrostatic capacity Cb. a stator including a stator iron core wound with a stator winding; the rotor disposed rotatably on a shaft, the rotor including a rotary body that holds a permanent magnet, and the shaft that extends through the center of the rotary body and joined to the rotary body; a bearing for supporting the shaft, the bearing including iron balls, an outer ring and an inner ring, and being provided with grease therein; and a conductive bracket for fixing the bearing, the rotary body has the ferrite magnet at an outermost periphery of the rotary body, and an outer iron core of a rotor iron core, the dielectric layer, and an inner iron core of the rotor iron core are disposed in this order toward an inside, the dielectric layer is a layer made of the insulating resin, and has a ring shape and is disposed between an inside and an outside of the rotary body so that the dielectric layer orbits around the shaft, and the rotary body is joined to the shaft at a joint inside of the inner iron core, the method comprising: setting a rotor-body electrostatic capacity Cr that is an electrostatic capacity between the shaft and an outermost wall of the rotary body by adjusting at least a width in a radial direction and a material of the dielectric layer of the rotary body, the method being characterized in measuring a bearing electrostatic capacity Cb that is an electrostatic capacity between the inner ring and the outer ring when the bearing is rotated at 1000 r/min; and in that the dielectric layer is set to be so adjusted that the rotary-body electrostatic capacity Cr is set smaller than the bearing electrostatic capacity Cb. setting a rotor-body electrostatic capacity Cr that is an electrostatic capacity between the shaft and an outermost wall of the rotary body by adjusting at least a width in a radial direction and a material of the dielectric layer of the rotary body, the method being characterized in measuring a bearing electrostatic capacity Cb that is an electrostatic capacity between the inner ring and the outer ring when the bearing is rotated at 1000 r/min; and in that the dielectric layer is set to be so adjusted that the rotary-body electrostatic capacity Cr is set smaller than the bearing electrostatic capacity Cb.