an electrical connection box is comprised of a wiring base group constituted by a minimum number of wiring bases required to realize a wiring pattern suitable to specifications of the connection box . each wring base includes a base body , wing portions provided on an outer periphery of the base body having end faces each formed with a coupling portion to which another wiring base of the same construction can be coupled , and guide portions integral with the wing portions and projecting circumferentially therefrom . in receiving a wire fed from a wiring head in a desired wire groove of the wing portions via a corresponding wire guide groove of the guide portions , the guide portion concerned prevents the wire from being dislocated from the wire groove , resulting in increased wiring speed , shortened wiring time and reduced manufacturing costs .