In this paper, a method for co-evolving morphology and controller of bi-ped humanoid robots is proposed. Currently, structure and walking pattern of humanoid robots are designed manually on trial-anderror basis. Although certain control theory exists, for example zero moment point (ZMP) compensation, these theories do not constrain structure of humanoid robot or detailed control. Thus, engineers has to design control program for apriori designed morphology, neither of them shown to be optimal within a large design space. Therefore, evolutionary approaches that enables co-evolution of morphology and control can be useful for designing the humanoid robot. Co-evolution was achieved in a precision dynamics simulator, and discovered unexpected optimal solutions. This indicate that a complex design task of bi-ped humanoid can be performed automatically using evolution-based approach, thus varieties of humanoid robots can be design in speedy manner. This is a major importance to the emerging robotics industries.