The invention provides an inorganic powder-containing resin composition capable of forming a dielectric layer having high light transmittance and excellent in surface smoothness. The invention also provides a film-forming material layer, a transfer sheet and a dielectric layer, which comprise the composition, a method of producing a substrate having a dielectric layer formed thereon, and a substrate having a dielectric layer formed thereon. The inorganic powder-containing resin composition comprises inorganic powder, a binder resin, and a phosphorus compound represented by formula (1): wherein R 1 , R 2 and R 3 independently represent H, an alkyl group, an alkylaryl group, NH 4 + (ammonium) or -(CH 2 CH 2 O) n -R 4 , wherein n is 1 to 15, and R 4 represents H, an alkyl group, an alkylaryl group or a (meth)acryloyl group.