We developed an unique device for measuring the viscosity of the liquids, using the mechanism of the tuning-folk vibration. This device has a pair of plate springs with a circular plate mounted on the end. When a pair of circular plate is operated in a sample by a resonance vibration in a reverse phase at a constant frequency, its amplitude is inversely proportional to the viscosity of the sample. So the viscosity can be obtained by measuring the amplitude. This device uses the standard liquid for calibration, and stores the calibration curve of the relationship between the amplitude value and the viscosity of standard sample. The rheologycal complicated materials can also be characterized by using this device.