In this paper, we describe the concept, design and implementation of a series of autonomous mobile soccer robots, named "Musashi" robot, which have a mechatronics modular architecture, to participate in the RoboCup middle-size league. In this design methodology, we show that the selection of a proper moving mechanism, a suitable vision system and a mechatronics modular architecture design can lead to realize a reliable, simple, and low cost robot comparing with most of car-like robots including many kinds of sensors and a complex design structure.