An assembly of a female connector, including: a housing including a casing having an opening formed in front of the casing so that a male connector is inserted in the opening, an internal body that includes one or more terminal-accommodating holes formed in the internal body and protrudes from a rear side of the casing towards a front of the housing, and a plurality of first combining portions that extend from the internal body to the front of the housing, each of the plurality of first combining portions including an extension groove formed in one side of each first combining portion so as to communicate with the one or more terminal-accommodating holes.