There are many robots which are controlled with PCs (Personal Computers) . Their typical OS (Operating System) was MS-DOS, but MS-DOS is not suitable for high level control. Therefore, RTLinux was developed as realtime OS. However, the authors tried to control mechatronic system by using common Linux and found that it has enough ability to control robots. In this paper, it is described why the common Linux can be used as OS for PCs that control robots. Some experimental results that indicate performance of common Linux as robot controlling OS are also provided. Then the control system developed for human type biped robot as an example that utilize this method is shown.