Auxiliary connectors (6) of a female connector (1) are formed for a plurality of types of female terminal fittings (8). When a plurality of auxiliary connectors (6) of the same type are mounted into a frame (2), the number of the terminal fittings to be inserted into the individual auxiliary connector (6) is decided based on connection loads per terminal fitting to ensure that an operation load of the auxiliary connector (6) does not exceed an upper-limit value, and the same number of terminal chambers (7) as the decided number of the terminal fittings are formed in the auxiliary connector (6). Thus, regardless of the specifications of the female terminal fittings (8), the female terminal fittings (8) can be mounted into all the terminal chambers 7 without exceeding the upper-limit value of the operation load of the auxiliary connectors (6).