An electrical connector set includes first and second connectors, in which the first connector has a first connection terminal, a first high-frequency connection terminal transmitting a high frequency signal, and a first external grounding member surrounding the first high-frequency connection terminal, the second connector has a second connection terminal, a second high-frequency connection terminal, and a second external grounding member surrounding the second high-frequency connection terminal. At a time of fitting, the second external grounding member is located on an inner side of the first external grounding member, the first and second connection terminals are located on an outer side of the first external grounding member, the second external grounding member is closed in a peripheral shape to surround the first and second high-frequency connection terminals, and first and second mounting parts are located on an inner side of the second external grounding member.