A cutting head attachment is attached to the front of an excavator. Cutting tools, called pick cutters, are arranged on the cutting head, and they grind the rocks or old building structures. When an excavator grinds cutting section, the drivinf torque fluctuates. Such fluctuation causes the reduction of performance and stavbility. A magnitude of the fluctuation changes depending on various design values, thus this study focused on work performance by several working postures.