A multilayer wiring board includes a main wiring board including insulation layers, first via conductors formed in the insulation layers, and a first conductive layer including first mounting pads such that the first mounting pads are positioned to mount a first electronic component and a second electronic component adjacent to each other on the main wiring board, and a wiring structure body mounted on the main wiring board such that the wiring structure body is positioned in an outermost insulation layer of the insulation layers, the wiring structure body including a second conductive layer which includes second mounting pads such that the second mounting pads are positioned to connect to the first electronic component and the second electronic component mounted on the main wiring board. The first via conductors are formed such that the first via conductors have diameters which increase in a same direction.