A multilayer wiring substrate mounted with an electronic component includes an electronic component, a core material layer having a first opening for accommodating the electronic component, a resin layer which is formed on one surface of the core material layer and which has a second opening greater than the first opening, a supporting layer which is formed on the other surface of the core material layer and which supports the electronic component, a plurality of connection conductor sections which are provided around the first opening and within the second opening on the one surface of the core material layer, bonding wires for electrically connecting the electronic component to the connection conductor sections, and a sealing resin filled into the first and second openings in order to seal the electronic component and the bonding wires.