An interposer includes an insulating substrate, a photosensitive dielectric film, a conductive layer, and a conductive via. The insulating substrate includes a bottom surface and a top surface, and defines a receiving through hole extending through the bottom surface and the top surface. The photosensitive dielectric film is mounted on the bottom surface. The photosensitive dielectric film defines a through hole spatially corresponding to and communicating with the receiving through hole. The conductive layer is mounted on an end of the photosensitive dielectric film away from the insulating substrate. The conductive layer covers an end of the through hole. The conductive via is received in the receiving through hole and the through hole. The conductive via contacts and electrically connects to the conductive layer.