RoboCup is a competition for autonomous robots playing soccer that makes contributions to various Intelligent Autonomous Systems. In RoboCup, frameworks to support robot programming are important because we have to resolve complex difficulties by software, especially in the four-legged robot league, where we can never resolve these difficulties by hardware since only fixed hardware is available. This paper describes an extensible framework which is suitable for advanced robot programming in the RoboCup domain. Our framework integrates a plug-in system and the scripting language Lua, which we embed in the system. In our framework, modules are freely replaced, without changing the bindings for the scripting language. Therefore, in our framework, even programming beginners can contribute to the development of huge, complex, robot programs without difficulty. Since many students who are not familiar with practical programming often join the team only a short time before the RoboCup competition, our framework is a good choice.