Recently, a lot of industrial robots are used in factories. But, in spite of spread of industrial robots, finishing robots like polishing robots are not widely used now. Because, to set parameters for pressing work piece to tool with appropriate force for force control robots are difficult. It is necessary to set various parameters according to process conditions. When the new polishing operation with different condition is executed, it is necessary to find and set new parameters. In this study, we aim to achieve the automatic task parameter setting system for polishing operation by robot arm. The task parameters of polishing operation which we selected are grain size of grindstone and the number of polishing times until final surface roughness. They are set based on the material of work piece and its required surface roughness accuracy. To realize the automatic task parameter setting system, we considered relation between each parameter and final surface roughness.