To improve the flame retardance, chemical resistance and heat resis tance of a polyphenylene ether after curing, while maintaining the excellent dielectric property, by incorporating curable polyphenylene ether resin compsn. and a dyestuff with a specific light absorption peak and a specific fluorescence yield.

A curable polyphenylene ether resin compsn. (A) is prepd. by blending a polyphenylene ether resin having a viscosity number (30°C, in a 0.5 g/dL chloroform soln.) of 0.1-1.0 with a thermoplastic or thermosetting resin, a radical initiator or a curing agent and a filler. One hundred pts.wt. of the component A is blended with 0.0001-5 pts.wt. of (B) a dyestuff having a light absorption peak at 350-480 nm and having a fluorescence yield of ≥0.1 to provide a curable resin compsn. This compsn. and a substrate (C) are blended to form a curable composite material wherein the total of the components A and B is 95-10 pts.wt. and the component C is 5-90 pts.wt. based on 100 pts.wt. of the total of the components A, B and C.