This paper describes the measurement of particle size distribution of TiO2 nano-particles in non-aquesous solvent by interactive force apparatus (IFA) under the electric field in order to suggest the application of the apparatus to the measurement of particle size distribution. The results were compared with results obtained from size measurement by SEM. The results show that the distribution measured by IFA at 0.03 and 0.06 V was larger (D50 = 430 - 480 nm) and at 0.12 - 0.48 V was smaller (D50 = 200 - 270 nm) than the one measured by SEM (D50 = 340 nm). The difference is mainly because small size fraction increased with increasing supply voltage. The results indicate that breakage of coagulated particles possibly occur due to electric breakdown. The electric breakdown was explained by curve fitting of two different particle size distribution functions with particle size distribution obtained from IFA measurement.