An electrical connector assembled component includes a first connector to be disposed on a circuit board and including a receiving portion; and a second connected to be accommodated in the receiving portion. The receiving portion includes a cylindrical receiving portion and an open receiving portion. The open receiving portion includes a locking piece connected to the side plate portion. The locking piece includes a locking portion at a front edge thereof. The cylindrical receiving portion includes an elastic contact piece. The second connector includes an elastic locking arm extending from the flat plate portion. The elastic locking arm is situated inside the cylindrical receiving portion at a position different from that of the elastic contact piece in the width direction, and at a position overlapped with that of the elastic contact piece in a vertical direction.