A multilayer wiring board with a built-in electronic component includes a substrate, a conductor layer formed on surface of the substrate, one or more electronic components positioned in a cavity formed through the substrate, an insulating layer formed on the substrate such that the insulating layer is formed on the component in the cavity, and a wiring layer formed on the insulating layer. The conductor layer has an opening formed such that the cavity is formed in the opening of the conductor layer and that the conductor layer has a first side in the opening and a second side in the opening on the opposite side across the cavity, and the cavity is formed in the opening of the conductor layer such that width between the cavity and the first side of the conductor layer is greater than width between the cavity and the second side of the conductor layer.