Hydraulic crushers are available in dismantlement circumstance for example office buildings. Because the crushers weigh 35 to 50kg, adopting new accessory functions were highly expected for saving work/worker and improvements on safety. In this study, an indoor dismantlement assistance machine, which could be stably controlled by a single worker, was developed and operability assessment was done. For operability assessment, two conditions: easy-to-move on (I).one direction, (II). every direction, are compared to evaluate the priority of work efficiency. First, notation system to combine the machine's Mobility Ellipsoid and the worker's Manipulating Force Ellipsoid into one ellipsoid (i.e. Workability Ellipsoid) was suggested. The Workability Ellipsoid describes the machine-head mobility distribution, and the major axis direction: its length varies with its viscosity resistance and the working posture. By adopting this feature, the crane arm's viscosity resistance and the working posture were decided.