To obtain a granulating method of a sheet-like synthetic resin material which has been hard to be granulated properly for blowing the material into a vertical metallurgy furnace such as a blast furnace.

A waste synthetic resin material is fractionated by its shape into a film-like synthetic material, a solid synthetic resin material, and a sheet-like synthetic resin material having an intermediate thickness of both the materials. The film-like synthetic resin material is shredded into small-pieces and, next, a melting/solidification granulation process 5 is applied thereto for forming resin particles (a) through a sieving and separating process 6. The solid synthetic resin material is subjected to shredding process 8, 10 to form synthetic resin particles (b) through a sieving process for separating iron debris or the like. Also, the sheet-like synthetic resin material is formed into sheet-like small pieces Co having the maximum dimension smaller than the maximum dimension of the film small pieces through shredding process 17, 19 followed by a melting and solidification granulation process 23 thereto. Then, synthetic resin particles consisting of the small pieces Co blended with the synthetic resin particles (b) are prepared. In this manner, blowing of the synthetic resim porticles can be done without giving adverse influences to operation of a vertical furnace such as blast furnace. Disposal of all waste synthetic resin bottle containers can also be done while contributing to the reduction of blast furnace costs.