Base on its experience as a leading robot user, DENSO developed a mobile robot designed for autonomous production system (APS). The APS is a new automated production system, where the concept is based on the characteristics of human-based assembly lines. One of the most important advantages of human-based assembly lines is flexibility, that is, the configuration of a production line can be rapidly changed according to the increase or decrease of production volume and period caused by market uncertainty. The flexibility is realized by autonomy, mobility and manipulation skill of a human. Therefore, we have developed mobile robots in order to construct the APS, which contains production machines, or mobile robots. The mobile robots equip autonomy, mobility and manipulation skill, and configure cooperative function, such as human social functions. Cooperative algorithm among robots is also addressed. The proposed cooperative algorithm is simple but efficient, and implemented in a practical line for an automotive starter assembly. As a result, we realized an automated production system that can change its production capacity between 4,700 and 61,000 units/month through fast transformation of the system structure.