In a surveillance system, a server and a plurality of cameras provided in a surveillance area are communicably connected to each other. The server includes a table memory that retains information on free resources of each of cameras. The server determines for each camera, a process to be executed by the camera, based on the information on the free resources of the camera, and transmits an instruction to execute the determined process to each camera. Each of the cameras executes a process corresponding to the instruction to execute, based on an instruction to execute the process transmitted from the server.