A lever (14) is pivotally movably supported on a female connector (11). In accordance with the movement of a slide member (13) relative to the female connector (11), the lever (14) is pivotally moved while held in engagement with a tongue portion (29b) of an engagement portion (29) formed on a male connector (16), and with this construction the inserting force is reduced. When the slide member (13) is completely drawn out relative to the female connector (11), an engagement projection (14g) of the lever (14) is engaged with an engagement claw (26a) of an elastic arm portion (26), and the lever (14) is held in this position. When a projection (29a) of the engagement portion (29) elastically deforms the elastic arm portion (26), the retained condition of the lever (14) is canceled, so that the lever (14) is allowed to be pivotally moved.