PURPOSE: To provide the titled compsn. having excellent dimensional accuracy and resistance to oils and heat, by blending a reinforcing agent with a thermo plastic resin mixture of an arom. polyphenylene ether resin, etc. and a polyethy lene terephthalate resin.

CONSTITUTION: 5W150pts.wt. reinforcing agent (e.g. glass fiber or silica) is blended with 100pts.wt. thermoplastic resin mixture of 20W80t% arom. polyphenylene resin (A) composed of a structural unit of formula I (wherein R1, R2 are a sterically non-hindering 1W4C alkyl, aryl, halogen, H) or said unit of formula I and a structural unit of formula II (wherein R3WR6 are each R1; one of R5 and R6 is always a group other than H) or copolymer thereof, or mixture thereof with a styrene resin such as a polymer obtd. from an arom. nonovinyl monomer of formula III (wherein R is lower alkyl, halogen; Z is R, H; p is 1W5) and 80W20wt% polyethylene terephthalate resin (B) having a crystal m.p. of 255W265°C and an intrinsic viscosity of 0.2dl/g (in o- chlorophenol at 25W30°C) represented by formula IV.