An imaging device includes an auto-focusing actuator, an image sensor, and a transparent dust-proofing member. The auto-focusing actuator includes a housing. The housing includes a top surface and an opposite bottom surface, and defines a through hole extending from the top surface to the bottom surface. A number of positioning rods extend from the top surface and cooperatively define a fixing space. The image sensor is mounted on the bottom surface of the housing and aligned with the through hole. The transparent dust-proofing member is mounted in the fixing space and seals the through hole.