A detection device includes a substrate, a light-emitter, and a light receiver. The substrate includes a first surface area and a second surface area, in which the first surface area has a first reflectance greater than a second reflectance of the second surface area. The light emitter is disposed on the first surface area, and the light receiver is disposed on the second surface area. The light receiver has a third reflectance which is substantially the same as the second reflectance of the second surface area.