Wiring substrate

A wiring substrate, comprising:

• a first wiring part comprising a first insulating layer and a first conductor layer laminated on the first insulating layer such that the first conductor layer includes a plurality of wirings configured to transmit high frequency signal;
• and
• a second wiring part formed on the first wiring part and comprising a second insulating layer and a second conductor layer laminated on the second insulating layer such that a thickness of the second insulating layer is smaller than a thickness of the first insulating layer and that a thickness of the second conductor layer is smaller than a thickness of the first conductor layer,
• wherein the first conductor layer in the first wiring part has a surface on an opposite side with respect to the first insulating layer such that an arithmetic mean roughness of the surface is smaller than an arithmetic mean roughness of a surface of the second conductor layer on an opposite side with respect to the second insulating layer, and the second wiring part is formed such that the second wiring part is positioned closer to an outermost surface of the wiring substrate than the first wiring part.