A circuit board which is used for a second electronic circuit laminated on the side of a first electronic circuit containing a high exothermic element, on which said high exothermic element is disposed, via said high exothermic element, in that: either (i) or (ii) below applies: (i) said circuit board comprises a substrate, which comprises at least one dielectric layer comprising ceramics, and at least one first surface electrode, which is formed on the side of said circuit board, facing said first electronic circuit, at least a part of conductor, which constitutes said at least one first surface electrode, is embedded inside of said substrate, said conductor, which constitutes said at least one first surface electrode, is exposed out of said substrate at least in a region of a first surface which is the surface of said circuit board, facing said first electronic circuit, and said region is opposed to at least one terminal of said high exothermic element, the thickness of said conductor, which constitutes said at least one first surface electrode, is not less than 100 micrometers in a direction perpendicular to said first surface, or (ii) said circuit board comprises a substrate, which comprises at least one dielectric layer comprising ceramics, and at least one first surface electrode, which is formed on the side of said circuit board, facing said first electronic circuit, and at least one layer of at least one inner layer electrode, which is embedded inside of at least one inner layer of said circuit board, at least a part of conductor, which constitutes said at least one first surface electrode, is embedded inside of said substrate, said conductor, which constitutes said at least one first surface electrode, is exposed out of said substrate at least in a region of a first surface which is the surface of said circuit board, facing said first electronic circuit, and said region is opposed to at least one terminal of said high exothermic element, the thicknesses of said conductor, which constitutes said at least one first surface electrode, and conductor, which constitutes said at least one inner layer electrode, are not less than 100 micrometers in a direction perpendicular to said first surface, and wherein the average thermal expansion coefficient of a first region, which is a sub-region of said circuit board between said first surface and a first boundary plane, which is a plane farthest from said first surface among planes parallel to said first surface and intersecting with a part of said conductor, which constitutes said at least one first surface electrode, embedded inside of said substrate, is larger than that of a second region, which is a sub-region not of said first region of said circuit board. (i) said circuit board comprises a substrate, which comprises at least one dielectric layer comprising ceramics, and at least one first surface electrode, which is formed on the side of said circuit board, facing said first electronic circuit, at least a part of conductor, which constitutes said at least one first surface electrode, is embedded inside of said substrate, said conductor, which constitutes said at least one first surface electrode, is exposed out of said substrate at least in a region of a first surface which is the surface of said circuit board, facing said first electronic circuit, and said region is opposed to at least one terminal of said high exothermic element, the thickness of said conductor, which constitutes said at least one first surface electrode, is not less than 100 micrometers in a direction perpendicular to said first surface, or (ii) said circuit board comprises a substrate, which comprises at least one dielectric layer comprising ceramics, and at least one first surface electrode, which is formed on the side of said circuit board, facing said first electronic circuit, and at least one layer of at least one inner layer electrode, which is embedded inside of at least one inner layer of said circuit board, at least a part of conductor, which constitutes said at least one first surface electrode, is embedded inside of said substrate, said conductor, which constitutes said at least one first surface electrode, is exposed out of said substrate at least in a region of a first surface which is the surface of said circuit board, facing said first electronic circuit, and said region is opposed to at least one terminal of said high exothermic element, the thicknesses of said conductor, which constitutes said at least one first surface electrode, and conductor, which constitutes said at least one inner layer electrode, are not less than 100 micrometers in a direction perpendicular to said first surface,