To obtain an excellent flame-retardant resin compsn. which has properties to prevent spread of fire too, while contg. no halogen. by compounding a specific thermoplastic resin, an inorg. flame retardant. an org.-solvent-sol. silicon polymer, and a compd. having specified solubility parameter and mol.wt.

This compsn. comprises a nonhalogen thermoplastic resin, an inorg. flame retardant, an org.-solvent-sol. silicon polymer, and a compd. having a solubility parameter of 8 or higher and a mol.wt. of 190 or higher. The silicon polymer has at least one R1O (wherein R1 is H or a 1-5C alkyl) group and at least one polysiloxane group per molecule, and the polysiloxane group has at least one Si atom bonded to the R1O group to form an Si-O-C bond and is bonded directly or indirectly to the main chain through an Si-C bond.