An attaching structure of an electrical wire cover (50) includes a lever (20) and a lock arm (45) engaged with a lock portion (55a). The lever is rotatably provided at a connector housing (10A), and engages the connector housing with a mating connector housing by rotating operation. The lever is held at a temporary-locking position before the engagement with the mating housing connector. An excessive displacement restriction portion (22a) is provided on the lever. The excessive displacement restriction portion comes in contact with the5 lock arm when the lever is held at the temporary-locking position so as to restrict excessive deforming of the lock arm in an outward direction.