An electrical connector is to be connected to a first mating connector and a second mating connector. The electrical connector includes a plurality of terminals; and a housing for holing the terminals in a terminal arrangement direction. The housing includes an upper housing and a lower housing attached to the upper housing. The upper housing includes a plurality of upper grooves for holding the terminals. Each of the upper grooves has an upper narrow width portion having a width smaller than other part of the upper groove. The lower housing includes a plurality of lower grooves for holing the terminal. Each of the lower grooves has a lower narrow width portion having a width smaller than other part of the lower groove.