It is preferable that at least one surface of second circuit 13 is a matte surface. In this case, one surface of second circuit 13 may be a matte surface and the other surface thereof may be a shiny surface, or both surfaces of second circuit 13 may be the matte surface. When the matte surface of second circuit 13 is disposed to face insulating layer 11, peel strength between second circuit 13 and insulating layer 11 in thick conductor built-in type printed wiring board 1 can be improved due to an anchor effect.

Ten-point average roughness (R_ZJIS) of the matte surface of the second circuit is not specifically limited, but ranges preferably from 0.5 μm to 5.0 μm, inclusive. Ten-point average roughness (R_ZJIS) of the shiny surface of the first circuit is not specifically limited, but ranges preferably from 0.5 μm to 2.5 μm, inclusive. On the matte surface, larger number of irregularities that are more precise than those on the shiny surface are formed as compared with the shiny surface.

Note that, in the exemplary embodiment, thicknesses T₁₃ of the plurality of second conductor wirings 13₁ to 13_m are same. However, the present disclosure is not limited thereto, and the thicknesses of the plurality of second conductor wirings may be different from each other as long as the thicknesses of the plurality of second conductor wirings ranges from 105 μm to 630 μm, inclusive. Also, in the exemplary embodiment, a cross-sectional shape of the plurality of second conductor wirings 13₁ to 13_m is a substantially trapezoid shape as illustrated in FIG. 1. However, the present disclosure is not limited thereto, and may be a trapezoid shape, a rectangular shape, a square shape, or the like.