Abstract: An automatic software updating method in a communication network including a host computer, a plurality of branch processing computers each connected to the host computer for serving as servers, and a plurality of personal computers connected to a corresponding branch processing computer is provided. The method includes the steps of: (a) uploading a new software together with a version-up table including a version code to the host computer; (b) downloading the version-up table uploaded in step (a) to the branch processing computer; (c) determining whether to download the software using the version code of the version-up table downloaded in step (b); (d) downloading the software according to the result of step (c); and (e) installing the software downloaded in step (d) in the personal computer. Therefore, an out-of-date software of computer systems dispersedly arranged in the network can be automatically updated by a partially corrected or newly developed software.