Because of the size of walking machines, scaled-down models having geometrical similarity can be used instead of full-scale models to measure energetic efficiency. First, to cope with this situation, five nondimensional parameters that control energetic efficiency Of walking machines are introduced for nine physical parameters by applying dimensional analysis techniques. Next, in order to check those influences on energetic efficiency, computer simulations are performed for an n-legged walking model. In these simulations, the influence on ground reaction forces is considered to satisfy the approximate balance of forces and moments when an overall walking machine assembly is assumed as a free body. Resultantly, several new facts are acquired from the viewpoint of similarity law.