Abstract: A device and method for optimally detecting the surface conditions of different types of wafers are disclosed. The device includes a light generating unit for impinging light on a wafer to generate a reflected light from the wafer, a combining unit including a plurality of filters having different light cut-off ratios for reducing the amount of the reflected light to generate a reduced amount of the reflected light depending on the reflection rate of the wafer, and a detection unit for processing the appropriately reduced amount of the reflected light to detect the surface condition of the wafer. A different filter or a different combination of the filters are selected depending on the reflection rate of the wafer being processed in order to appropriately reduce the amount of reflected light to be processed by the detection unit.