To provide a method and a device capable of accurately sorting even if sorting object materials have small particle diameters.

The method comprises impressing a high-voltage to a vibrating electrode plate 3a, sloping at a predetermined angle, and on an electrostatic electrode plate 5b, placed over the electrode plate 3a through a separation space 6, to form an electrostatic field in the separation space 6, supplying electrostatically charged multiple kinds of plastic particles to the separation space and vibrating the electrode plate 3a upward in the sloping direction, attracting and biasing plastic particles charged in antipolarity with the electrode plate 3a to the electrode plate 3a by static electricity of the electrostatic field to convey them upward in the sloping direction. The plastic particles electrostatically charged in homopolarity with the electrode plate 3a are repelled and biased by the electrode plate 3a by static electricity of the electrostatic field and conveyed downward in the sloping direction by gravity and separated in accordance with kinds of plastics.