This is a study on cooperative work to be done by organizing a team of two workers. An assumption was made that work time of a team is affected by the following three factors : work time of each worker, conversation made in a team during work and the level of satisfaction each worker obatins from his work. Based on this assumption, experiments were made and results were analyzed. The analysis indicated that, if work assignment is the same, work time of a group is affected by these factors to the different degrees, depending on a role-making (work method) applied by a team.