Receiving portions (26, 27) for partial locking and full locking are formed on walls of a retainer mount hole (24) in a housing (10). The receiving portions (27) for full locking are before the receiving portions (26) for partial locking with respect to an inserting direction of a retainer (30). Resiliently deformable holding arms (35A, 35B) for partial locking and full locking are cantilevered on the retainer (30), and locking sections (41, 42) resiliently engageable with the corresponding receiving portions (26, 27) are formed at the free ends of the holding arms (35A, 35B). The holding arms (35A) for full locking extend in the inserting direction of the retainer (30) from their supported ends to their free ends, whereas the holding arms (35B) for partial locking extend in a direction opposite from the inserting direction of the retainer (30) from their supported ends to their free ends.