In this paper, we propose an adaptive resource control method for multiple resource real-time systems. Execution results of applications are evaluated as a QoS level and a fair QoS management is an important issue. The fair QoS level depends on the number of active applications and their characteristics so that it may change dynamically due to the current states of the real-time systems. The proposed controller activates at discrete times and updates resource allocations to achieve the optimal fair QoS level. Moreover, the algorithms used in the controller solve the update in O(mn) time per its activation. We derive sufficient conditions for achievement of the fair resource allocation. Simulation experiments show that a fair resource allocation can be achieved under the conditions.