PURPOSE: To enhance dielectric characteristics, heat conductivity and dimensional stability by forming an insulating layer from a specific cured polyphenylene ether resin.

CONSTITUTION: In a laminated sheet wherein an insulating layer is laminated to a metal base, said insulating layer is composed of a polyphenylene ether resin and satisfies 40≥R×100≥7(%) in the area ratio R of 3.5-dimetylphenol and whole methylphenol on the basis of the analysis due to pyrolytic gas chromatography. Further, the extraction ratio of said cured polyphenylene ether resin when said resin is treated with chloroform for 12 hr at 23°C is 0.01-20wt.% and this chloroform extractive polyphenylene ether resin containes a unit represented by formula (I) (wherein R1, R2, R3 and R4 may be the same and different and are a hydrogen atom, an aryl group or a propagyl group and at least one of R1R4 is a group other than hydrogen).