A lever (60) is formed with a resiliently deformable lock arm (71) projecting substantially along a rotating direction of the lever (60). A housing (20) is formed with a base piece (27) standing in a direction crossing a connecting direction to a mating connector (90). An engaging portion (35) for holding the housing (20) and the mating connector (90) in the properly connected state by being resiliently engaged with a leading end part of the lock arm (71) is formed on a leading end part of the base piece (27). A recess (33) into which a finger (50) is insertable to disengage the engaging portion (35) and the lock arm (71) is formed in a base end part of the base piece (27).