PID control has been mainly used over the past years among various kinds of modern processes, however, the advanced control for most recent industrial processes is playing a more important role that leads to resource saving, energy conservation, and upgrading. 0n the other hand, most personnel operating or maintaining machines are unaccustomed to deal the advanced control because of its complexity. For that reason, we propose the simple design method of the sliding-mode control (SMC) for such processes with time delay. The proposed method is the sliding-mode control using a disturbance observer with compensation for the "pade-approximation error" that does not satisfy the matching condition. Moreover, we propose the optimal pole assignment algorithm of the observer. The advantages of the proposed method are 1) good transient characteristics, 2) reduction of chattering, 3) high robust performance, and 4) simplicity in designing. Simulation and experimental results illustrate the effectiveness of the proposed method with applying to the cooling plate for semiconductor manufacturing.