It is aimed to smoothly connect connectors by absorbing assembling variations between the connectors. A first spring piece (24) and a pair of second spring pieces (27) are deflectably provided in a holder portion (H) to resiliently sandwich a first connector (6) in a Y-axis direction. The second spring pieces (27) are formed with upper receiving surfaces (29) symmetrically inclined along an X-axis direction so that resilient forces act on both receiving portions (18) of the first connector (6) toward a center axis along the X-axis direction. Further, the first connector (6) is held in a state displaceable also in a Z-axis direction in the holder portion (H). This causes the first connector (6) to be held at a reference position and held in a three-dimensionally displaceable state.