A transfer device includes an image bearing member, a transfer member, a test image detector, and a shield member. The image bearing member bears a toner image on a surface thereof within an image forming area. The transfer member disposed opposite the image bearing member forms a transfer nip between the transfer member and the image bearing member through which the recording medium is conveyed and transfers the toner image from the image bearing member onto the recording medium in the transfer nip. The test image detector disposed downstream from the transfer nip in the direction of conveyance of the recording medium detects a density of a test image for adjustment of toner density formed outside the image forming area. The shield member disposed between the test image and the transfer member shields the test image from an electrical field generated between the image bearing member and the transfer member.