PURPOSE: To remove foreign matter such as heavy metals and their compds. contained in grain such as rice by using this method and device.

CONSTITUTION: A voltage is impressed between the first and second conductors 1200 arranged close to grain 100 (rice) and a variable voltage part 30 for impressing a voltage between the first and second conductors 1200 to generate an electric field 300 passing through the grain 100 are provided to this device. A specified voltage is impressed on the grain 100, and the foreign matter in the grain 100 is separated and removed from the grain 100 by the electric force of the electric field 300.