PURPOSE: To contrive to improve the sorting work and crushing efficiency by a method wherein a plurality of plastic materials, which are made separable by thermally shrinking used plastic bottles, are sorted in response to their qualities of material and finally sorted plastic materials are respectively crushed.

CONSTITUTION: Plastic bottles are sent with a feeding conveyer 1 to a heating device 2 so as to be thermally shrunk by being sprayed with heated water during their transport under rotation. At this time, the fitting state of a stand to a PET bottle main body is disengaged by the difference between their thermal shrinkage factors due to the difference between their qualities of material. Further, metal caps easily come out. Furthermore, the plastic bottles go to small pieces through thermal shrinkage. After that, transparent bottles, green bottles and stands are sorted manually and sent through a large number of chutes 4, which are arranged at both sides of a sorting conveyer 3, onto respective conveyers 5aW5c so as to be ground to the predetermined sizes with grinders 6aW6c in order to be sent to filling machines 15aW15c for sacking by means of air chutes 7aW7c.