A circuit board is provided. The circuit board includes a substrate, a waveguide line and a laminated waveguide. The waveguide line is at least partially positioned on a first surface of the substrate. The waveguide line transmits a high frequency signal. The laminated waveguide is formed inside the substrate. The laminated waveguide is electromagnetically coupled to the waveguide line, and has a lead-out portion led out from inside the substrate to a surface other than the first surface. The laminated waveguide includes a dielectric layer, a pair of main conductive layers and a through conductor group. The pair of main conductive layers sandwiches the dielectric layer in a thickness direction thereof. In the through conductor group, a plurality of through conductors are arranged along a high frequency signal transmitting direction. The plurality of through conductors electrically connect the pair of main conductive layers.