Alpha Camera is developed as a remotely-operated detector to check the alpha contamination of wastes generated during decommissioning of Fukushima Daiichi Nuclear Power Station. The smear method is currently used to check the alpha contamination inside the plant. However, a large amount of waste will be generated from future decommissioning. Therefore, in order to reduce the exposure of workers, a remotely-operated alpha detector with wide range is needed. In this paper, to confirm that the Alpha Camera can measure alpha contamination of floors and equipment in the plant, we measured concrete with different roughness of surface mounted with 241Am unsealed radiation source. As a result, different detection sensitivity depending on the roughness of surface was confirmed, even if the same amount of α- nuclides were attached.