This study discusses the cost allocation for the cooperative project on construction of regional information technology in terms of utility maximization method. It is assumed that the joint investment organization including municipal concerns promotes the regional optical fiver network systems in the area where it is disadvantageous for enterprise compared with the advanced area. The case study was executed in the Tokachi River Basin where the existing basic fiver networks are allocated. Here, the utility functions of the agents that participate in the project are formulated due to multiplier manner. In order to find the optimal cost of each agent, Genetic algorithm was adopted. The project can be operated appropriately due to evaluating the maximum utility of the comprehensive formulation in the cooperative system.