The existence of subak as a traditional irrigation system in Bali has tri hita karana as its philosophy and focus on social and cultural activities. The more complex of its members’ needs and problems, government has endeavored to develop subak orienting business. One of the business is run by the farmers’ cooperative. The objectives of this study are to describe the potential economic activities of subak, and to portrait the institutional adjustment of subak toward the business orientation. The collected data was analyzed by employing descriptive method. The study pointed out that the subak of Guama has great potential to establish and develop cooperative due to the previous economic activities, such as being a channel on the agri-inputs distribution, and making deposit and money lending to members. The institutional adjustment of subak is done through the set-up of organizational structure of cooperative under the subak system. The head of subak is a controller of the management of cooperative established. The regulations of subak is very effective to support the good performance of cooperative. Members of subak who are also members of cooperative could get economic benefits from the cooperative.