In any physical systems, there inevitably exists time delay. Since it has very characteristic and distinctive properties, control of time delayed systems is even now a very difficult and unresolved problem. Therefore a lot of researches about time delay have been studied so far. A distinguished time delay compensation method is Smith predictor. It can equivalently eliminates time delay from closed control loop and stabilize time delayed systems. However precise delay time model is needed for implementation of the method. It is therefore necessary to measure accurate delay time. In these circumstances, authors have proposed a novel time delay compensation method based on the concept of network disturbance (ND) and communication disturbance observer (CDOB). In this method, delay time model is not needed. It is therefore not necessary to measure delay time. Hence it can be flexibly applied to many kinds of time delayed systems. In this paper, a design method of time delayed control system based on the concept of ND and CDOB is proposed. Dynamic property of ND leads to derivation of two design conditions of CDOB. Then actual design procedure of CDOB based on derived design conditions is presented. The validity of proposed design method is verified by experimental results.