Provided are a fixed-focus photographing module, a manufacturing method thereof, and a focusing device and method thereof. The focusing method includes: pre-assembling an optical lens assembly in a lens assembly holder, wherein the optical lens assembly is exposed at the exterior of the lens assembly holder, and the optical lens assembly is located in a photosensing path of a photosensing component assembled in a circuit board to form a pre-assembled photographing module; performing, by the pre-assembled photographing module, a photographing operation to obtain a testing image; adjusting, according to the testing image, a relative position between the optical lens assembly and lens assembly holder until the pre-assemble photographing module outputs a clear image as required; and fixing the optical lens assembly and the lens assembly holder to complete a focusing operation and obtain an assembled fixed-focus photographing module.