It is difficult to say that the low temperature heat (50-100 °C, e.g. factory exhaust heat or hot spring) is used effectively at present. Problems in use are unstableness of supply and low temperature, it is desirable to gather up by heat-storage and use it. The purpose of this study is the viscosity evaluation of nanosuspensiton type latent heat storage material. Tetracosane (CH3(CH2)22CH3 = 338.66, purity > 99%, melting point 50.6°C: Ref.) is used for dispersion material as a latent heat storage material of nanosuspension. The nanosuspension consists of tetracosane as the dispersed latent heat storage material, the distilled water and the non-ion surfactant. The latent heat storage material is dispersed averaged diameter about 250 nanometers in continuous water phase by an ultrasonic homogenizer. This paper deals with the viscosity including non-Newtonian characteristics that estimated by using a rotary viscosity meter (ThermoScientific, HAAKE Viscotester550). The measuring ranges are shear rate < 500 1/s and temperature 10-84 °C. Experimental data is adjusted by an exponential law, and useful experimental correlation equations are obtained.