Holonic Manipulator has electronic devices such as control computers and sensors among its local mechanical components. This manipulator design has three major advantages: reduction of wire harness between devices, high software productivity, and fault tolerability of the system. In this paper, first two actually developed Holonic Manipulators are represented. Then a simple structure model especially focused on the mass of the constituent components is developed so that the efficiency ratio of the payload mass to the manipulator's own mass can be analyzed. This ratio shows a slower increase consistently with the payload mass due to the DC servomotor mass/power characteristic and mechanical structure mass/stress characteristic. Fused structure design is employed mainly between heat sinks or support members of the computer and mechanical structure. Improvement of the efficiency ratio by fused design is estimated with the model using the mass fusion function.