A skin diagnostic device is provided that includes a body including a coupling member positioned on one surface, the body being attached/detached to/from an electronic device including an image sensor by using the coupling member, an optical unit positioned in the body and including at least one lens, wherein the optical unit is configured to focus measurement light reflected from a target on the image sensor of the electronic device, and at least one light source unit positioned adjacent to the optical unit and configured to irradiate light toward the target, wherein the coupling member includes at least one magnetic body and an alignment member positioned adjacent to the magnetic body.
