PURPOSE: To clean a molding machine efficiently by purging the machine with a thermoplastic resin compound in which a fibrous filler of 2mm or more in length is mixed in an amount of 10-80wt.% of the compound.

CONSTITUTION: A purging material of a resin compound in which a fibrous filler of 2mm or more in length is mixed with a thermoplastic resin in an amount of 10-80wt.% of the compound is added into a molding machine. The molding machine is purged by plasiticizing the purging material with rotating the screw. In this process, the fibrous filler in the purging material is entangled into a cotton shape to effect brushing, scraping off deposits on the screw and cylinder of the machine. The deposits scraped off are incorporated into the cotton-shaped filler to be discharged from the machine.