Multilayer printed circuit board and manufacturing method thereof

The purpose of the present invention is to provide a multilayer printed circuit board which mitigates the problems of ''warping'', ''twisting'' and ''changing size'' seen in printed circuit boards obtained by the conventional build-up method, and to provide a manufacturing method thereof. In order to achieve this purpose, a multilayer printed circuit board is adopted which is provided with two more build-up wiring layers on both sides of a core substrate, wherein said core substrate is provided with an inner layer circuit on both sides of the skeletal material-containing insulation layer, the insulation layer being 150mum thick or less, wherein the X-Y direction linear expansion coefficient of the skeletal material-containing insulation layer is 0ppm/DEG C-20ppm/DEG C, a first build-up wiring layer and a second build-up wiring layer provided on both sides of the core substrate comprise a copper circuit layer and an insulating resin layer having an X-Y direction linear expansion coefficient of 1ppm/ DEG C-50ppm/DEG C, and the relation holds that the ratio of the value of the X-direction linear expansion coefficient (Bx) and the value of the Y-direction linear expansion coefficient (By) of the insulating resin layer is 0.9-1.1.