An electronic component device includes a cored wiring substrate, an electronic component, a reinforcing layer, a connection terminal, and sealing resin. The cored wiring substrate includes a core layer. The electronic component is mounted on the cored wiring substrate. The coreless wiring substrate is disposed on the cored wiring substrate and the electronic component. The reinforcing layer is provided in the coreless wiring substrate and in a region corresponding to the electronic component. The connection terminal connects the cored wiring substrate and the coreless wiring substrate. The sealing resin is filled between the cored wiring substrate and the coreless wiring substrate.