A board mating connector which includes a ground unit in which a tapered portion is formed, the board mating conductor comprising: a signal contact unit which has one side in contact with a signal electrode of a board and is electrically connected to the signal electrode; a ground contact unit which has one side in contact with a ground electrode of the board and is electrically connected to the ground electrode; and a dielectric unit which is disposed between the signal contact unit and the ground contact unit, wherein the ground contact unit includes a first ground portion having a first ground hollow portion and a second ground portion of which the other side is partially inserted into the first ground hollow portion and which has a second ground hollow portion, characterized in that: the first ground portion includes a first ground tapered portion formed on a wall thereof so as to have an inclined shape such that an inner diameter thereof is gradually decreased toward the other side thereof, and the second ground portion has the other end in contact with the first ground tapered portion and is relatively moved, wherein, when the second ground portion is moved in a direction parallel to the longitudinal axis of the board mating connector from an extended position towards a retracted position, the other end of the second ground portion is compressed by the first ground tapered portion, and wherein the compressed other end of the second ground portion is restored in a direction in which an inner diameter of the first ground tapered portion is increased so that the second ground portion is moved in a direction parallel to the longitudinal axis of the board mating connector from the retracted position towards the extended position. a signal contact unit which has one side in contact with a signal electrode of a board and is electrically connected to the signal electrode; a ground contact unit which has one side in contact with a ground electrode of the board and is electrically connected to the ground electrode; and a dielectric unit which is disposed between the signal contact unit and the ground contact unit, wherein the ground contact unit includes a first ground portion having a first ground hollow portion and a second ground portion of which the other side is partially inserted into the first ground hollow portion and which has a second ground hollow portion, characterized in that: the first ground portion includes a first ground tapered portion formed on a wall thereof so as to have an inclined shape such that an inner diameter thereof is gradually decreased toward the other side thereof, and the second ground portion has the other end in contact with the first ground tapered portion and is relatively moved, wherein, when the second ground portion is moved in a direction parallel to the longitudinal axis of the board mating connector from an extended position towards a retracted position, the other end of the second ground portion is compressed by the first ground tapered portion, and wherein the compressed other end of the second ground portion is restored in a direction in which an inner diameter of the first ground tapered portion is increased so that the second ground portion is moved in a direction parallel to the longitudinal axis of the board mating connector from the retracted position towards the extended position. the first ground portion includes a first ground tapered portion formed on a wall thereof so as to have an inclined shape such that an inner diameter thereof is gradually decreased toward the other side thereof, and the second ground portion has the other end in contact with the first ground tapered portion and is relatively moved, wherein, when the second ground portion is moved in a direction parallel to the longitudinal axis of the board mating connector from an extended position towards a retracted position, the other end of the second ground portion is compressed by the first ground tapered portion, and wherein the compressed other end of the second ground portion is restored in a direction in which an inner diameter of the first ground tapered portion is increased so that the second ground portion is moved in a direction parallel to the longitudinal axis of the board mating connector from the retracted position towards the extended position.