An optimization system has a plurality of nodes, each including: a calculation processing unit that calculates an optimum value of a determination variable representing a parameter that controls the nodes by using the ADMM; and a function value calculation unit that receives an input of a value of the determination variable and calculates the value of the objective function based on a calculation model constructed by a learning processing. An arbitrary value of the determination variable is input to the function value calculation unit, and the calculation processing unit substitutes the value of the objective function calculated by the function value calculation unit and the arbitrary value of the determination variable into a second optimization problem by dual transformation of the first optimization problem, thereby repeatedly executing a processing of calculating a value of the dual variable until the value of the dual variable satisfies a predetermined condition.