In this paper, a standard robot design methodology is suggested and a software architecture for modular robot is introduced. The robot is modularized by several functions, and the module is produced according to a standard proposal. Each module requires standard interface for communicate in distributed environments. Software architecture was developed to support distributed component environment, and application development support tools are developed for user convenience. Many robot softwares are developed in a library form so that, they are being used widely robot application software development. Also a device driver was developed for the mostly used sensor and actuator. It is verified that the modular robot can be applied in various fields through guide, errand and guard scenario.