This invention provides a multilayer printed wiring board which achieves fine pitches. A heat resistant substrate is incorporated in a multilayer printed wiring board and interlayer resin insulation layer and conductive layer are placed alternately on the heat resistant substrate. A built-up wiring board in which respective conductive layers are connected by via hole is formed. A via hole is formed on the surface of a mirror-processed Si substrate by using a heat resistant substrate composed of Si substrate so that finer wiring than a resin substrate having unevenness in its surface can be formed, whereby achieving fine pitches. Further, by forming the wiring on a mirror processed surface, dispersion of wiring decreases thereby decreasing dispersion of impedance.