A surveillance system is provided. The surveillance system includes: a first frequency communication module configured to receive a first surveillance image from a first camera, and receive a second surveillance image from a second camera; a second frequency communication module configured to receive second frequency communication module notice information from the second camera; and a processor configured to change a reception signal gain value of the first frequency communication module based on the second frequency communication module notice information, wherein a reception signal strength of the first surveillance image is different from a reception signal strength of the second surveillance image.