A circuit board structure for a low noise block down-converter is disclosed. The circuit board structure is used for transmitting a first radio-frequency signal and a second radio-frequency signal across each other, and includes a first substrate and a second substrate. The first substrate includes a first wire for transmitting the first radio-frequency signal, a first grounded wire formed in parallel to a side of the first wire, and a second grounded wire formed in parallel to another side of the first wire. The second substrate is electrically connected to the first substrate, and includes a second wire for transmitting the second radio-frequency signal, a third wire formed on a side of the second wire and a fourth wire formed on another side of the second wire.