A separation method includes: conveying a separation subject comprising a group of pieces placed on a conveyor in one direction; detecting, by a detecting device, compositions of pieces in the group of pieces placed on the conveyor; generating, by a blower, airflow at an end portion of the conveyor in a conveying direction in which the conveyor conveys the separation subject, the airflow having a velocity matching or substantially matching a conveying speed of the conveyor; stabilizing the airflow by a current plate placed along a trajectory of the group of pieces; and by a jetting device, obtaining position information of a piece of a particular material detected, and jetting pulse air toward the piece of the particular material when the piece of the particular material, which is travelling through air from the conveyor and whose travel is assisted by the airflow, passes by the jetting device.