It is introduced that the development of GPS based small mowing robots. The mowing robots will be expected to work at open areas like as parks. To work in the open area, the robots must keep the safety for people at first. Therefore, the robots are developed using the platform, based on the Robomower RL500, to make advantage keep safety for people. However, the performance of the small robots will become insufficient for the mowing task. In addition, several control issues arise in the practical field including obstacle avoidances and escape from stuck areas. To cover the properties of the small robots and control issues in practical world; multi-robots approach is applied. Namely, using the multiple robots, the cooperative task sharing is applied for executing the mowing task sufficiently.