MULTILAYER WIRING SUBSTRATE AND PRODUCTION METHOD THEREFOR

To improve the degree of freedom of design of a multilayer wiring substrate incorporating therein an electronic component. A multilayer wiring substrate 1 includes a first layered structure including conductor layers 13, 14, 15, and 16, and insulation layers 23, 24, 25, and 26 including therein via conductors 33, 34, 35, and 36 each having a diameter which decreases from the upper surface of the insulation layer toward the lower surface thereof; an electronic component 51 embedded in the first layered structure; and a second layered structure stacked on the first layered structure, and including conductor layers 17 and 18, and an insulation layer 27 including therein a via conductor 37 having a diameter which decreases from the upper surface of the insulation layer toward the lower surface thereof.