A tremor is somewhat rhythmic motion that may occur in various body parts. An essential tremor is one of the most common tremor disorders of the arm and it may occur during a voluntary motion. If the essential tremor occurs in the arm, the person may not be able to achieve the target task properly since the human performs various sensitive tasks with certain tools. Suppressing the vibration of the grasped tool is important when the person uses the tool. Power-assist robots are useful for not only the physically weak persons but also for persons involved in physically-taxing work such as a care or a farm work. Although some power-assist robots are controlled by using electromyogram (EMG) signals, EMG signals are influenced by the essential tremor. Therefore, when the user who suffers from the tremor uses the power-assist robot controlled based on EMG signals, the robot might assist the vibration of the tremor. In this paper, the tremor suppression control method is proposed for upper-limb power-assist robot. In proposed method, the vibrations of the hand and the tip of the tool are suppressed. The validity of the proposed method was verified by the experiments.