An electrical connector for high-frequency transmission comprises an elongate insulative housing including a top wall and a bottom wall opposite to each other, and a pair of end walls respectively connecting two ends thereof, and a receiving cavity surrounded thereby; a terminal assembly received in the top wall and the bottom wall respectively, and stacked in an up-to-down direction; and a metal case enclosing the insulative housing; wherein the terminal assembly includes a signal terminal group, and a ground terminal group including a first contact portion and a second contact portion, wherein the first contact portion and the second contact portion are arranged in a front-to-back direction perpendicular to both the up-to-down direction and the elongate direction, and respectively protruding into the receiving cavity.