To again reutilize a thermoplastic resin constituting electric and electronic machineries or the like as parts of similar electric and electronic machineries or the like.

In a manufacturing method for a regenerated plastic material, a molded part obtained by injection-molding a virgin thermoplastic material is used as a raw material to manufacture the regenerated plastic material. This manufacturing method includes a production process for producing a regenerated raw material from the molded part, and a melting and kneading process for melting and kneading the regenerated raw material and an extrusion method for extruding the melted and kneaded regenerated material by an extruder. In a screen mesh used in the extrusion process, a screen mesh having a mesh of No.120 of a Test Sieve US Standard or a mesh finer than the same or having a mesh of No.200 or a mesh coarser than the same is used.