To provide a plastic static separation method for improving separation performance by controlling the temperature in a separator.

In a separator for crushed refuse to be separated composed of plastic in which static electricity is used, a humidity sensor 11 for sensing the relative humidity in a separator (box 10) and a dehumidifier 12 to be actuated for setting the relative humidity in the box 10 sensed by the humidity sensor 11 at the set humidity are provided, and the relative humidity in the box 10 is set to 60% or lower, by which crushed refuse 1 to be separated an be separated and the separation capability can be kept to separate stably the crushed plastic refuse 1 to be separated.