There is provided a method of manufacturing a semiconductor substrate. The method includes: (a) forming a wiring pattern on a substrate; (b) covering the wiring pattern with an insulating resin, thereby forming a first insulating layer; (c) forming a second insulating layer on the first insulating layer; (d) forming a plurality of grooves through the second insulating layer; (e) forming at least one via hole through the first and second insulating layers by irradiating at least one of the grooves with a laser beam; (f) forming a seed metal layer on an inner surface of the at least one via hole, inner surfaces of the grooves, and a surface of the second insulating layer; and (g) forming a plating layer in the at least one via hole and the grooves, by an electrolytic plating using the seed metal layer as a power feeding layer.