A socket connector includes an insulating housing, at least one docking element, a plurality of docking terminals, a fastening board and an outer cover assembly. A middle of the insulating housing has at least one holding groove. The at least one docking element is assembled in the at least one holding groove. The at least one docking element defines a plurality of docking grooves. The plurality of the docking terminals are fastened in the plurality of the docking grooves, separately. The fastening board has a first opening. The insulating housing is fastened to a rear surface of the fastening board. The outer cover assembly is assembled in the first opening. The outer cover assembly includes a frame and a waterproof element. The waterproof element has a sleeving ring, a covering portion, and a connecting element connected between the sleeving ring and the covering portion.