The main purporse of this paper is to study on the influence of temperature effect on electrical-properties, i.e., dielectric breakdown voltage, dielectric constant and resitivity of homemade insulating oil containing antioxidant. Transformer oil manufactured in Korea is taken for a sample, and this sample is classified into seven samples in which antioxidant is contained and not contained, and antioxidant is divided into three kinds of amount: 0.3%, 0.5%, 0.8%. Changing the tempe5rature of the samples by oil bath, the electric properties measured from the samples are as follows: (1) the variation of either the dielectric breakdown voltage or the resistivity are considerably large, but the dielectric constants are almost unchanging. (2) In view of electrical characteristic, the deterioration rate of the samples containing antioxidant is somewhat lower than that of other samples. (3) Nearly the same value is shown in the dielectric-breakdown voltage of the samples, in which contained the different amount of antioxidant: 0.3%, 0.5%, 0.8%, but the decrease rate of resitivity is lowest, 0.3%, of all. As the result of the experiment, This study can suggest that 0.3% be the optimum amount of antioxidant which will be added transformer oil manufactured in Korea and is useful for the understanding about the electrical properties of transformer oil containing antioxidant.