To obtain a resin composition which can give a product excellent in mechanical properties, flame retardancy, bleed out resistance upon treatment with dry and wet heat, point contamination resistance, etc., by compounding a PS resin with a plurality of aromatic phosphates having specified melting points and a silicone compound in a specified ratio.

This composition comprises 100 pts.wt. PS resin, 5-12 pts.wt. aromatic phosphate mixture comprising (x) pts.wt. aromatic phosphate having a melting point of 90°C and represented by formula I (e.g. a compound of formula V) and (y) pts.wt. aromatic phosphate having a melting point of below 90°C or having no melting point (e.g. a compound of formula VI) in a y/x ratio of 0.25-0.5 and 0.2-4 pts.wt. silicone compound. In the formulae, R1 to R8 are each H or a 1-5C alkyl; Ar1 to Ar4 are each phenyl or a phenyl substituted with a halogen-free organic residue; X is a group of any one of formulae II to IV; Y is a direct bond, O, S, SO2, C(CH3)2, CH2, CHPh; Ph is phenyl; (n) is 0 or greater; (k) and (m) are each 0-2; and k+m=0-2.