Receptacle connector

A receptacle connector of a substrate-to-substrate connector unit that electrically connects substrates by fitting the receptacle connector mounted on one of the substrates and a plug connector mounted on another of the substrates to each other, comprising:

• a housing in which a recess for housing the plug connector is formed, the recess opening at a side opposite to a surface mounted on the substrate;
• a required number of contacts arranged between end portions of the housing;
• and reinforcement metal fittings each of which is provided on one of the end portions of the housing,
• wherein
• the reinforcement metal fitting has a cantilever resilient piece that extends in an arrangement direction of the contacts, and a contact piece that extends from a free end portion of the cantilever resilient piece and comes into contact with the plug connector when the receptacle connector and the plug connector are fitted to each other.