To make it possible to improve the grounding property of a conductive shell with a simple configuration.Connector-side ground connecting members (ground spring pieces) 24c provided in a conductive ground shell 24 of a receptacle connector 2 and board-side ground connecting members (rear holddowns) 24b are disposed such that they extend approximately in parallel with a fitting direction of a plug connector 1 serving as a fitting mate for the receptacle connector 2, and ground currents flowing between the connector-side ground connecting members 24c and the board-side ground connecting members 24b take the shortest straight courses so that occurrence of electrical loss or an undesired inducing phenomenon is substantially suppressed.