In the literature, mobile robots featuring both omni-directional and rough-terrain mobility are typically realized by heavy and complicated mechanisms. In considering real outdoor applications, such as hazardous site-inspections or scientific investigations, however, it is desired to develop small and light-weight robots by focusing on the mechanical simplicity and toughness. The primary objective of this study is to investigate and to realize an omni-directional mobile robot on unpaved rough terrain by small, light-weight, simple mechanism. For this purpose, we propose a new concept of wheel structure as well as an omni-directional moving robot. The new wheel, named globular metal spring wheel and composed simply of several super-elasticity-material rods, has not only omni-directional functionality but also properties of light weight, mechanical simplicity and external shock absorbing function. With this globular wheel, a new omni-directional mobile robot, “Eggbeater”, is also developed to evaluate the mobility performance. This paper presents our proposal and development of the globular metal spring wheel and the omni-directional rough-terrain mobile robot, and discusses performance evaluation experiments.