An electronic component is provided between at least two wiring boards. An electrode of the electronic component is electrically connected to at least one of the wiring boards. Also, the wiring boards and are electrically connected to each other. Additionally, the gap between the wiring boards and is sealed with a resin. The electronic component built-in substrate is featured in that a bonding pad formed on one of the wiring boards and is electrically connected to an electrode of the electronic component by a bonding wire, and that at least a connection portion between the electrode of the electronic component and the bonding wire is coated with a protection material.