Pivot shafts are formed on a female connector, and male and female connectors are fitted together by pivotally moving an operating lever pivotally mounted on the pivot shafts. The operating lever has shaft-receiving grooves for respectively receiving the pivot shafts, and includes retaining portions formed integrally with this operating lever, and each of the retaining portions has a flat or curved abutment surface which is in line-contact with the associated pivot shaft received in the shaft-receiving groove, thereby retaining the pivot shaft in the shaft-receiving groove.