A printed wiring board includes a first conductor layer including a first conductor circuit and a second conductor circuit formed adjacent to the first conductor circuit, a resin insulating layer formed on the first conductor layer such that the insulating layer is filling space between the first and second conductor circuits, and a second conductor layer formed on the insulating layer such that the insulating layer is interposed between the first and second conductor layers. The first conductor layer has thickness in the range of 1 μm to 15 μm and is formed such that the space between the first and second conductor circuits has width in the range of 2 μm to 7 μm, and the insulating layer includes inorganic particles having average particle diameter in the range of 0.05 μm to 1.0 μm and content in the range of 35 wt. % to 75 wt. % in the insulating layer.