A connector includes: a socket having a socket fitting body provided with socket terminals; and a header having a header fitting body provided with header terminals. At least one of a sidewall surface on an inner side of the socket fitting body and a sidewall surface on an outer side of the header fitting body includes a protrusion in which at least one side surface of the both side surfaces in the width direction faces the corresponding opposite surface formed in the sidewall surface of the other fitting body with the socket and header fitting bodies fitted to each other.