Provided is a board-to-board connector including a housing having a protrusion, one or more signal terminals held on the housing such that a contact portion is exposed to the side of the protrusion, a high-frequency signal terminal arranged outside an end portion of the protrusion, and a shell surrounding an outer peripheral portion of the housing and made of a conductive metal material. In the board-to-board connector, the shell integrally includes a GND terminal portion having a plate-shaped board-side shielding portion arranged on a bottom portion outside the end portion of the protrusion and a plate-shaped GND terminal body standing on the protrusion-side end of the board-side shielding portion and arranged closer to the protrusion with respect to the high-frequency signal terminal, and a high-frequency signal terminal housing hole in which the high-frequency signal terminal is arranged is formed in the board-side shielding portion.